The latest act of IRA decommissioning has failed to persuade David Trimble to back moves to re-establish devolution in Northern Ireland.

But talks are continuing in a bid to overcome the latest problems and end the confusion into which Ulster's politics has again descended.

Earlier on Tuesday, there had been an announcement of fresh elections to the Northern Ireland assembly and the news that a large quantity of IRA arms has been destroyed.

The Ulster Unionist leader and former first minister said he had initially been "very much encouraged" by resulting comments made by Sinn Fein's Gerry Adams.

But Trimble said his party had been looking for a "transparent" act of IRA decommissioning, and the latest moves had failed to deliver it.

"We had made it very clear to republicans and indeed to the governments and to General de Chastelain that what we needed in this situation was a clear, transparent report of major acts of decommissioning of a nature which would have a significant impact on public opinion and demonstrate that we were in a different context," he said.

"Unfortunately we have not had that. We have not had that at all. There may possibly have been those substantial acts of decommissioning, but we have not had the transparency or an adequate report on it."

The UUP leader said he was putting "on hold" the sequence of events that had been due to clear the way for elections to the Northern Ireland assembly.

He said republicans should now seek to "repair the damage that has been done" by their failure to be clear about the IRA's decommissioning.

Delivering a brief assessment of the situation to journalists gathered in Belfast, the prime minister later said that "virtually everything" had been agreed except for the details of the decommissioning process.

Tony Blair said the two governments would now be "spending that extra bit of time in order to get the thing done".

Irish premier Bertie Ahern said they would work to overcome the latest "obstacle".

"We have to try to see if we can find a way, and we will," he said.

A sombre Gerry Adams later said he "did not know" how the sequence of events could now be put back on track in the short time available to the parties.

Tuesday's events began with a government announcement that elections to the devolved assembly will now take place on November 26.

After the date was announced the IRA revealed it had authorised "a further act of putting arms beyond use" and would seek to destroy its arms "at the earliest opportunity".

And decommissioning chief General John de Chastelain later confirmed that light, medium and heavy ordnance and ammunition, including explosives, had been destroyed or put beyond use.

He said that a "considerably larger" quantity had been put beyond use than during the two previous tranches of IRA decommissioning.

"It is more than we had in the first two events and we are going to press for more," said de Chastelain.

The Canadian general said the IRA had declined to reveal specific details of the quantities put beyond use - a decision that prompted the UUP ire.

But the international body is maintaining contact with an IRA representative who appears to have indicated that further disarmament could follow "at the earliest opportunity".

The moves came after Ulster Unionists and Sinn Fein appeared to have brokered a deal following weeks of intense negotiations.

Number 10 confirmed the election move early on Tuesday following "a lot of intensive discussions" between key players in the province.

Tony Blair arrived in Belfast on Tuesday where he met for lunch with his Irish counterpart Bertie Ahern.

Downing Street said initially that "potentially this could be the most significant day in Northern Ireland since the Good Friday agreement".

The two premiers had been due to issue a statement later on Tuesday, but the latest events have left that in doubt.

Sinn Fein chief Gerry Adams earlier committed his party to building a "stable society" through "an end to conflict".

Whilst he stopped short of saying the war was over, his commitment to "exclusively" peaceful and democratic means will be enough to reassure moderate unionists.

The Sinn Fein chief vowed to fight for a united Ireland through the ballot box.

"We have sought and we are seeking to change minds and attitudes," he said. "We are totally committed to building this peace process."

Making the Good Friday Agreement work was "a collective responsibility" which required trust on all sides, added Adams in a carefully coded message to dissident republicans.

"I appeal to them to join with the rest of us, republicans and unionists, nationalists and loyalists, in taking a leap forward together and collectively building a new future based on justice and peace," he said.

"For our part Sinn Fein is totally committed to establishing an entirely new, democratic and harmonious future with our unionist neighbours."