The Ulster Unionist Party leader, Mr David Trimble, could have lost a vote on returning to the Executive with Sinn Fein by a margin of 70-30 had the Ulster Unionist Council meeting gone ahead tomorrow as originally planned, senior political sources have estimated.
Divisions are likely to intensify within the party over the coming week as Mr Trimble campaigns for support for the restoration of the North's political institutions.
The campaign by Mr Trimble to reverse the position inside his party is expected to focus on what are seen as the positive aspects of the recent IRA statement, especially the undertaking to put weapons "beyond use".
The UUP leader said last night, "Guns beyond use means decommissioning. Decommissioning means permanently unusable, permanently inaccessible."
However, the chief critic of Mr Trimble's policy inside the party, Mr Jeffrey Donaldson, queried this interpretation of the IRA statement, which had come from the British Prime Minister but not from the IRA itself.
"Have the IRA clarified what they mean by putting guns beyond use?" Mr Donaldson asked on UTV. "P. O'Neill, that mythical figure, has been silent for the last week."
Sources close to the UUP leadership cautioned that Mr Trimble could not be expected to sell the Hillsborough deal on his own. He would need active public backing from others in the party.
The position of the UUP deputy leader, Mr John Taylor, remained unclear. He is said to control about 8 or 9 per cent of the delegates' votes.
It will probably be critical for Mr Trimble to have Mr Taylor's full support, but other senior figures in the party will have to back the leader as well. There is considerable doubt over Mr Trimble's continued leadership if he loses the vote at the rescheduled UUC meeting on May 27th.
The Northern Secretary, Mr Peter Mandelson, said Mr Trimble had made the right decision in postponing the UUC meeting.
He said he would rather wait a week for a "good result" than rush forward now. "David Trimble has been clarifying some issues and driving a hard bargain over others, and now he needs time to present the outcome to his party.
"I am confident he will be successful and that we will be able to restart the institutions after this short delay." Mr Mandelson said nationalists and republicans who wanted progress would understand the need for a "breathing space" for unionists.
"The IRA statement that followed the two governments' statement at Hillsborough breaks new ground. People should have the time and space to consider the full significance of this step forward. I would rather wait a week for a good result than rush forward now."
Members of the UUP Assembly team gathered at Stormont's Parliament Buildings yesterday morning amid continuing uncertainty. Mr Trimble was said to have taken soundings at the meeting which were broadly encouraging and he was thought to have a majority of UUP Assembly members.
At one stage in the afternoon, it seemed he would declare his public support for the Hillsborough deal and his determination to fight for its acceptance at the UUC meeting, which was at that stage still expected to go ahead tomorrow.
Downing Street was said to be monitoring the level of support for Mr Trimble closely and political sources indicated that the uncertainty over Mr Taylor's views was probably decisive in the decision to postpone tomorrow's meeting by one week.
It is understood the UUP leadership informed the two governments and the main nationalist parties of the postponement before it was announced. Over the coming week London and Dublin are expected to provide any support possible to Mr Trimble, particularly by stressing the constitutional benefits for unionism of the full implementation of the Belfast Agreement.
Observers said that, provided there were no more concessions by London on issues such as policing in the coming week, the republican movement would remain quiescent, hoping that Mr Trimble would be successful.