Mr Seamus Mallon has said he was forced into a public disagreement with Mr David Trim ble on decommissioning and the formation of a shadow executive after the First Minister failed to turn up for a prearranged meeting last Monday.
Mr Mallon, the North's Deputy First Minister, said he had made his views clear in private that decommissioning was "most certainly not" a precondition to the formation of an executive.
"I could not have done any more in terms of informing him of my position, and it was unfortunate that he was not there on Monday for the meeting we had both arranged," Mr Mallon said on RTE Radio. He hoped the Ulster Unionist leader would attend a meeting with him today.
Mr Mallon emphasised the damage being done to the political process by the decommissioning issue and said that he would be putting this to the British Prime Minister, Mr Tony Blair, when he meets him at the Labour Party conference in Blackpool this week.
"I will be putting it clearly to him that, in my view, the decommissioning issue is continuing to poison the body politic. I will be putting it to him that, if that continues, then there are great difficulties," Mr Mallon said.
Mr Trimble will also be meeting Mr Blair.
A Sinn Fein spokesman said the party's president, Mr Gerry Adams, might travel to Blackpool, although no meeting had yet been arranged.
Mr Mallon said he believed there was "a way of getting a process devised" to get around the problem of decommissioning. This would involve the two governments, all the parties and the chairman of the International Decommissioning Body, Gen John de Chastelain.
He said that this process could be "timetabled and scheduled in a way that it wasn't as amorphous as it is now and that there was some definition on it". He wanted the issue to be taken out of the political equation "by means of an understanding of how it is going to be dealt with".
Mr Mallon also called on Sinn Fein to make a move on decommissioning and said there was a requirement in the Belfast Agreement for the party to do this. "We in the nationalist community have sought confidence-building measures from the British government. They are in the agreement. Is it not now time to give this very substantial confidence-building measure to the unionist community?"
Responding to Mr Mallon's comments, a Sinn Fein spokesman said the party had made it clear that it could not deliver IRA decommissioning or any timetable or schedule.