The Taoiseach has described the statement by Gen John de Chastelain about IRA decommissioning proposals as a "historic breakthrough".
Mr Ahern said the Government "warmly welcomes the agreement between the Independent International Commission on Decommissioning and the IRA on the method of putting arms completely and verifiably beyond use".
This "very, very significant" development represented a major step towards a resolution of the arms issue, and "I think it also gives us a way of moving towards a full implementation of the Good Friday agreement".
The Taoiseach was speaking on RTE Radio 1's lunchtime news. "It is a historic breakthrough," he said. "Other things have to happen out of it admittedly, but I'll be confident that that will happen."
Mr Ahern believed the statement "clearly" was enough for the peace process to continue. "And hopefully over the next number of days, perhaps the outstanding issue of the commencement of that process hopefully will also move on and that will allow us to get on with the full implementation of the Good Friday agreement, which brings in all of the other issues of policing, demilitarisation and the stability of the institutions," he said.
Calling on all the Northern political parties to "reflect carefully on the significance of it", Mr Ahern said: "The question they may ask is did this proposal initiate a process and that of course means that it has to happen or start happening.
"Obviously David Trimble and his colleagues and others would want to see that the process commences, but the process for that is between the general and the IRA representative and the fact that the international commission has issued this statement today speaks for itself."
Asked what the next step would be, he said: "Gen de Chastelain said the proposals initiate a process that would put IRA arms completely and verifiably beyond use. I think people will say that they would like to hear that that process has started. And I think that question arises. But that is not a matter that I have any call on. It is a matter clearly between Gen John de Chastelain and the IRA representative."
Mr Ahern said of the Ulster Unionist Party: "Well, I think they should reflect very carefully on this statement. I think I've signalled the issue that will create some concerns for them but I think they should see the enormous move of this statement, the significance of it.
"Hopefully, the implementation of it will commence. I'm sure that will be of concern to them, but I think John de Chastelain, having brought it to this stage, will bring it the remaining way and people should see the historic significance rather than trying to see difficulties in it."
The start of the process was a matter for the commission, which had worked on this for six or seven years. "But they have painfully negotiated with a lot of the paramilitary groups over a long period and they always have been determined that they would only issue positive statements when they believed there were significant and substantive moves."
Of yesterday's statement, he said: "I think as always they're very clear. They say that in the negotiations with the IRA representative that they have proposed a method for putting arms completely and verifiably beyond use and that this proposal meets the commission's remit in accordance with the Government's schemes and regulations and that they believe that this starts a process that will put arms completely and verifiably beyond use.
"So I think that fulfils the criteria that we have tried to work on, really back since the spring of 1995."
Asked if he believed Mr Trimble should put himself forward again as first minister, Mr Ahern said: "Well, clearly what we've been working to do is to get things back to where they were." It was, he said, "very important that we get back to a situation where David Trimble is there, Seamus Mallon is there and that the Sinn Fein ministers to the Executive get on with their work".
