Speaking at a rally on Sunday to mark the anniversary of the 1916 Easter Rising against British rule in Dublin, he described demands for the republican paramilitary group to disarm as a "provocation".

And senior Sinn Fein negotiatior Mitchel McLaughlin said the peace process was "in crisis".

But First Minister of the Northern Ireland assembly David Trimble gave a quite different message - predicting an IRA weapons handover within weeks.

Andy Tighe reports on events around the most important weekend in the Republican calendar

The deadline for setting up an executive for the assembly passed on Good Friday, 2 April, without an agreement on the stumbling block issue of paramilitary weapons.

A "declaration", intended as a basis for a solution to the impasse over decommissioning, was issued last week by UK Prime Minister Tony Blair and his Irish counterpart Bertie Ahern.

The Ulster Unionists - the assembly's largest party - are refusing to sit with Sinn Fein on the executive unless the IRA begins to hand over some of its weapons.

Gerry Adams: "There can be no veto for anyone in this process"

All the parties have until next week to discuss the declaration and decide whether or not they accept it.

At the Dublin rally Mr Adams paid tribute to the IRA, saying: "I commend today's IRA volunteers. 1916 was an IRA uprising.

"One of the provocations has been the demand on the IRA to disarm. This is something which the IRA has made clear it feels under no obligation to do."

The Sinn Fein leader has made it clear that there is little room for manoeuvre on the issue of paramilitary weapons, although he said he had assured Mr Trimble that he will do his best to find a way out of the impasse.

Gerry Adams: No obligation

In addition, he will meet the Irish prime minister for talks before next week's deadline and it is rumoured that the IRA's "army council" will also convene soon to discuss the declaration.

Despite moves by Sinn Fein on Saturday to distance itself from the declaration, Ulster Unionist leader Mr Trimble was quoted in the Sunday Times as saying he believed republicans would accept it.

"I think we have cracked it now," he said. "There are still some things to be done but we are getting into the foothills now and the road is getting easier."

David Trimble: Optimistic

Responding to Mr Trimble's comments, Sinn Fein negotiator Mitchel McLaughlin insisted nothing had changed the fact that decommissioning was not a pre-condition in the Good Friday agreement.

And he accused Ulster Unionists of losing their nerve over the implementation of the deal.

"There is no agreement and the process is stalled, and rather than write articles that give the wrong impression, people would be better reconvening the talks to resolve this problem," he told BBC Radio 5 Live.