David Trimble's speech to his party conference was a disappointment to all of us who want to see the institutions agreed on Good Friday put in place and further progress made towards a lasting peace.

David Trimble appears to be saying that he is not now prepared to honour the commitments given on Good Friday. Instead, he has declared his intention to block the institutions which would begin the process of turning the promise of the agreement into the reality of a new approach based on inclusivity and equality and involving, crucially for nationalists, all-Ireland structures.

It appears that the political leadership of unionism, in all forms, remains wedded to a failed and unworkable status quo. The unionist parties are opposed to change and seek to prevent change, either by outright opposition to the agreement or by hollowing out its potential to deliver change.

Inertia in the process serves the strategic interests of unionism.

In contrast, nationalism, in all its forms, remains wholeheartedly committed to this process of change. For over 10 years now Sinn Fein's primary focus as a political party has been our peace strategy and the development with others of a process to resolve the causes of conflict and deliver a lasting peace settlement.

Since the first joint statement by Gerry Adams and John Hume in April 1993, which publicly kick-started the peace process, we have collectively made significant progress towards that objective. Who could have imagined then that we would have had the IRA cessations and inclusive negotiations, much less an agreement and its endorsement by the vast majority of the people of Ireland?

The progress we have made resulted from hard work and determination and a willingness to take risks and initiatives.

But at all times the process has had its detractors, those who are only involved reluctantly and begrudgingly. There are also those who remain outright in their opposition to the process and its agenda for change.

Unfortunately, therefore, the progress we have made to date and the potential for further progress generated by the Good Friday Agreement cannot be taken for granted.

The agreement is not a peace settlement. Nor indeed does it purport to be one. Rather, it is an important staging post of the peace process which can, like others before it in recent years, create the conditions for further movement in that direction.

The agreement itself has not resolved the causes of conflict, but it has mapped out a political and institutional framework within which many of the causes of conflict can be addressed.

Specifically and in categoric terms it makes provision for the establishment of inclusive political institutions, including all-Ireland institutions, as the political foundation on which to build.

Other vitally important issues were addressed but not resolved. Instead, mechanisms by which this might prove to be possible were agreed. Among these are human rights, policing, justice, equality in all its dimensions, decommissioning and the demilitarisation of society.

But to listen to David Trimble one would think that decommissioning was the only issue yet to be resolved. Unionists have sought to rewrite the actual provisions of the agreement on this issue by superimposing their own positions on the matter.

They have deliberately developed a crisis in the process itself by refusing to co-operate in the establishment of the political institutions agreed and by using the decommissioning issue as an excuse for this. They have sought to obscure other issues of central importance to a just and lasting peace.

No one should be in any doubt about how strongly nationalists feel about unionist militias - the RUC and the RIR - who still patrol our streets. Or a justice system which has perpetuated the repression of nationalists for generations. Or the system of pervasive inequalities which have rendered nationalists second-class citizens. Or the denial of human rights across the whole spectrum of issues. Nor should they doubt how central the resolution of these issues is to a lasting peace settlement.

But Sinn Fein has not made any one of these a precondition to progress. All of these are key issues which must be politically resolved if we are to effectively remove the causes of conflict and build a lasting peace settlement. They are indispensable objectives of an evolving process.

All require resolution. But for any party now to make any of these important issues a precondition to the implementation of the institutional provisions of the agreement is an act of bad faith which breaches and therefore threatens the entire agreement.

At this point what is required, as agreed, is the establishment of the political institutions. That is the next staging post.

The refusal to establish the Executive and the all-Ireland Ministerial Council and the associated implementation bodies cannot be viewed as an isolated blip in the implementation of the agreement.

This is not a difference of interpretation or emphasis. It is in fundamental conflict with the provisions of the agreement. It is undemocratic and a denial of the rights and wishes of the vast majority of the people of Ireland who voted for the agreement on May 22nd this year. The refusal to establish the political institutions agreed has blocked progress.

But a conflict-resolution process cannot stand still - it is either moving forward or it is moving back. And this process is certainly not moving forward at present. This must be a matter of deep concern for everyone.

Central to Sinn Fein's peace strategy is the development of a credible and effective way of achieving political change through peaceful and democratic methods. Collectively, we have constructed a peace process, which has already delivered cease-fires by all the main protagonists, with the obvious exception of the British state forces.

Sinn Fein played a key role in delivering the total and unequivocal cessation by the IRA last July, but fundamentally it was the firm and binding political commitments given that inclusive negotiations would begin that allowed us to convince the IRA that they should restore their cessation of military operations.

The value of that initiative by the IRA should not be underestimated. The fact that the guns are not now in use is of immense significance. It underlines the IRA commitment to the search for a lasting peace settlement.

It created the conditions for further progress towards that objective.

The key to ensuring that progress is made lies in the creation of the required political conditions. That is a collective responsibility. Rather than exploring this sensible option, however, the opposite is now happening.

The refusal to establish the political institutions and the resurrection of the demand for decommissioning as a precondition to excuse this strengthens and encourages the rejectionists, makes our task more difficult, undermines our position and strengthens the positions of those that argue that politics cannot deliver real change.

Sinn Fein is committed to the wholehearted implementation of the Good Friday agreement in all its aspects, including the provisions on decommissioning. But the greatest threat to all of this is the resistance to change within unionism generally and, most critically, within the UUP leadership. In effect, a unionist veto on progress has been resurrected.

What is required at this time is that David Trimble makes a choice. He is either for the agreement of Good Friday or he is against it. If he is for the agreement, he must implement it. He was awarded the Nobel Peace Prize on that basis. He must defend it against its critics and he must tackle the rejectionists, including those within his own party.

The peace process is not the property of any one party. The UUP, however, seems to have difficulty in working with a process which is not strictly under its control or an agreement which is not strictly on its terms.

They have, in essence, a problem with equality and inclusivity, and decommissioning has become the current excuse for this.

When the IRA announced their first cessation in 1994 the response of the then British government was to demand decommissioning to prevent the commencement of inclusive negotiations in the full knowledge that the IRA would not surrender.

Unionists seized on this demand as a tactical means to obstruct and delay the process of change which has flowed from the peace process itself.

It should also be remembered that, if unionists had had their way, their demands for decommissioning would have prevented the second IRA cessation, would have prevented inclusive negotiations and would have blocked the Good Friday agreement. The response of the political leadership of unionism throughout has been variously obstructive, negative and reluctant.

Is should be remembered that most of the numerous political initiatives over the recent past have been taken by Sinn Fein unilaterally or as part of the wider political leadership of nationalist Ireland.

Sinn Fein's peace strategy evolved over a 10-year period. In our Towards a Lasting Peace document, published in 1991, we argued for the creation of a peace process and identified the measures for it to succeed.

Along with other leaders of nationalist Ireland we played a key role over a period of years in creating the conditions which allowed us to persuade the IRA to call a unilateral cessation of military operations in 1994 and to reinstate this in 1997. The disciplined maintenance of the IRA cessation was a significant contributory factor to the negotiation of the Good Friday agreement.

In September 1994, before the Mitchell Principles were conceived, our party president, Gerry Adams, pledged in conjunction with John Hume and the then Taoiseach, Albert Reynolds, our total commitment to democratic and peaceful methods of resolving political problems.

We engaged positively with the International Body on Decommissioning in 1995 and 1996 in an attempt to resolve the impasse created by John Major's demands for an IRA surrender.

Despite the self-evident bad faith of the Major government we used our influence to sustain the first IRA cessation for a full 17 months until the rejection by John Major of the report of the International Body on Decommissioning.

Republicans worked tirelessly throughout the summer of 1996, deploying our most senior party members on the ground, night after night, to calm the situation and to positively influence the response of the nationalist community to the Six County-wide events surrounding Drumcree. Likewise, in July 1997, when the British government and the RUC literally trampled over the rights of nationalists on the Garvaghy Road, we acted decisively.

We continuously took political initiatives in this period, often with John Hume, to put the peace process back on track, and succeeded in this in 1997.

In September 1997 we affirmed our commitment to the Mitchell Principles.

Throughout the talks process we participated constructively in the work of the liaison sub-committee on decommissioning.

From December 1997 to February 1998 we worked tirelessly to keep the process on track in the face of the concerted loyalist murder campaign which saw 11 nationalists killed and almost 100 wounded in shooting attacks.

Since the Good Friday agreement we have continued to use our influence positively to effect its full implementation. We secured our party support for the agreement in both referendums. Despite the risk of a destabilising effect on our own constituency we sought, and secured, our party's support to amend our constitution and removed a 75-year ban on members taking seats in any Northern assembly to allow us to participate fully in the new institutions established in accordance with the terms of the agreement.

In the run-up to President Clinton's recent visit we took a series of initiatives to help move the situation out of the political vacuum caused by the failure to implement this stage of the agreement. On September 1st Gerry Adams repeated Sinn Fein's commitment to make conflict a thing of the past, emphasised that inclusive and honest dialogue is the only way forward for this country and unequivocally set out our belief that the violence we have seen must be for all of us now a thing of the past - over, done with and gone. That statement, along with my subsequent appointment as Sinn Fein's representative to work with the IICD, were welcomed and acknowledged as important political initiatives and confidence-building measures by the US President, Bill Clinton, An Taoiseach, Bertie Ahern, and the British Prime Minister, Tony Blair.

Unfortunately, these initiatives did not have the intended effect of ending the current political impasse. Rather than acknowledging and responding to these initiatives and employing them to energise the support he has within his own party, within the unionist population and within the North in general for the agreement, David Trimble disappointed everyone by his begrudging and ungenerous response.

Instead, he retreated once again into the sterile politics of demanding decommissioning to block progress.

Sinn Fein appreciates that David Trimble has problems within his own constituency. Indeed, we have been careful not to exacerbate these difficulties. But we all have problems. The difference is that Sinn Fein and Irish republicans have faced up to these problems. In our approach to the negotiations we listened to the experiences of those involved in the South African peace process. This was a benefit which all of the parties to the negotiations enjoyed.

The South Africans emphasised the importance of internal communication and dialogue. In effect, the need for an internal communication with our own constituency. We expended more time, energy and personnel on this aspect of the negotiations than on any other and stretched the Irish republican constituency to the limit in the process.

And not without taking damage or suffering defections. The republican constituency can go no further.

It is becoming clear that David Trimble sees the impasse, generated by his refusal to implement the next stage of the agreement, as an opportunity for unionism to rewrite the Good Friday agreement by skilfully utilising the divisions in unionism in an attempt to renegotiate the agreement.

It is increasingly my opinion that he does not want to implement it and that he has changed his position on the agreement since Good Friday. He is introducing new demands and conditions designed to exclude Sinn Fein, despite our electoral mandate, and to dilute the inclusivity and equality which underpins the agreement.

And in so doing he is excluding every elected representative and attempting to nullify every vote cast. David Trimble is making a last ditch attempt to rewrite the agreement on unionist terms.

But the Good Friday agreement is not solely a unionist agreement. It is the collective product of inclusive negotiations. It is premised on a willingness to accept our political opponents on their own terms - as they are rather than how we want them to be.

On May 27th the overwhelming majority of the people of Ireland stamped their ownership on it. The agreement cannot be retrospectively rewritten on the basis of unionist demands, preconditions or vetoes.

I am, however, concerned that the UUP strategy for rewriting the agreement is having a negative effect on some of the parties to the agreement and at the threat this poses to the agreement itself.

There is a collective duty on all of us who negotiated and endorsed it to defend and ensure its implementation. The two governments have a particular responsibility, in their overseeing role, to ensure that the agreement is implemented in full.

The people of Ireland are democratically entitled to see the structures agreed on Good Friday, and endorsed in subsequent referendums, established without further delay. Sinn Fein is democratically entitled under the terms of the agreement to Executive office and to places on the all-Ireland Ministerial Council.

So, too, are all other political parties with a sufficient mandate from the electorate. These are mandatory provisions of the agreement. They are not subject to the discretion of Mr Trimble.

David Trimble holds the position of First Minister only as part of automatic power-sharing arrangements. If there is no Executive, selected on the basis of proportionality, then there can be no First Minister.

If there is no Executive or all-Ireland Ministerial Council, then there can be no Assembly. David Trimble cannot pick the elements of the agreement with which unionism is comfortable and ignore the others. He cannot overrule the votes of the majority of the people of Ireland. He cannot unilaterally rewrite the agreement or assert a veto over its implementation.

The two governments are primarily responsible for ensuring that the provisions of the agreement are implemented, in the terms and within the time-scales agreed on Good Friday.

The test for the two governments, and for the agreement itself, is whether these democratic rights will be defended and acted upon.

Human rights, policing, justice, equality, decommissioning and demilitarisation are all issues which can and will be dealt with, and the agreement makes provision for addressing all of these matters.

What concerns people now is that the peace process continues, that the guns are not in use, that the agreement is built upon and that we continue on the road to a lasting peace settlement.

The establishment of the political institutions agreed on Good Friday is the specified and essential next step for taking that agenda forward, the next staging post which can change the political context in which all of the unresolved issues can be dealt with.

Martin McGuinness MP is Sinn Fein's chief negotiator in the talks on decommissioning. This article is also published today in the Irish News