Talks continued after the setback over decommissioning
Elections in Northern Ireland will be held without agreement to move the process forward, the Ulster Unionist leader David Trimble has said.
Speaking ahead of a meeting of the party's executive on Monday, Mr Trimble said that although progress had been made, time had run out for an agreement on a power-sharing executive to be reached ahead of elections on 26 November.
Earlier on Monday, Sinn Fein accused the UUP of walking away from the current phase of the political process.
However, Mr Trimble rejected the suggestion.
"It is not right to say that we were not prepared to proceed even at a very late hour," he said.
"We did put proposals which, if I was to receive in the course of the next couple of hours a clear indication that those proposals were now operational, it is a different matter entirely, we would roll with them."
Negotiations have, so far, failed to bridge the gap between Ulster Unionist demands for clarity over the IRA's third arms move and the IRA's reluctance to spell out in more detail exactly what weaponry has been decommissioned.
Sinn Fein President Gerry Adams said he was bitterly disappointed that Mr Trimble had decided to abort the process.
"He may be engaged in a little bit of damage limitation but it is obvious Mr Trimble isn't prepared to go forward, he made that clear last Tuesday" he said.
"We could have walked away, we could have engaged in a blame game, we could have been giving vent to the righteous anger that is out there."
Meanwhile, a meeting of the Ulster Unionist Council to discuss a possible deal with republicans over "acts of completion" has been cancelled.
Elections to the assembly are taking place on 26 November
The meeting, due to be held on Wednesday night, was cancelled following a meeting of party officers in Belfast on Monday.
UUP chairman James Cooper said that "as there has regrettably been no progress, the meeting is off".
SDLP leader Mark Durkan said both the Ulster Unionists and Sinn Fein were "walking away from the Good Friday Agreement".
"As the days go by, it is looking more and more unlikely that the problem parties, Sinn Fein and the UUP, are going to overcome their difficulties," he said.
"And it seems more and more likely that they are going to walk away from their commitments under the Agreement - to work the institutions and to end paramilitarism."
However, DUP deputy leader Peter Robinson said he believed there would be very different negotiations after the elections.
"I think at that stage there will be a realisation that after a one year suspension of the institutions - after it having collapsed on four occasions that the Belfast Agreement has failed and that we need new structures," he said.
"The Democratic Unionist Party has made it very clear that we are prepared to negotiate a new agreement, an agreement that will have bring stable and lasting political structures for Northern Ireland.
The Ulster Unionists and Sinn Fein held lengthy talks over the weekend, in an attempt to achieve what Prime Minister Tony Blair has called a "positive atmosphere" in the run up to the elections.
Last week, Mr Trimble called for greater clarity on the details of decommissioning in General John de Chastelain's report.
The arms chief said the number of IRA weapons put beyond use had been "considerably larger" than before.
Despite the setback, Northern Ireland Secretary Paul Murphy made an order to enable fresh elections to take place.
The devolved administration was suspended a year ago amid allegations of IRA intelligence-gathering in the Stormont government.
Mr Blair and Taoiseach Bertie Ahern have been in contact with the key players over the weekend, along with British and Irish officials
Mr Blair's chief of staff Jonathan Powell has been in Northern Ireland.
President George W Bush's special envoy Richard Haass has also been involved in diplomatic efforts.
General de Chastelain is not expected to return to Canada until later this week.
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