The anti-Agreement Ulster Unionist MP, Mr Jeffrey Donaldson, is seeking a meeting with his party leader today to discuss tomorrow's Ulster Unionist Council meeting.
Mr David Trimble will be urging UUC delegates to support a return to government with Sinn Fein. Mr Donaldson will be opposing this proposal and will be tabling an amendment.
Mr Donaldson last night said he was requesting a meeting with Mr Trimble to see if there was any way of avoiding tomorrow's "divisive vote". He said many delegates were very concerned the UUP would be badly damaged.
The anti-agreement MP denied he was concerned the vote would go against the No camp and expressed confidence that his position would be widely supported. The deal on decommissioning and devolution was totally inadequate, he said.
An actual start to decommissioning, leading to total disarmament and the disbandment of the Provisional IRA, was needed. Another anti-agreement UUP MP has described Mr Trimble's support for returning to government with Sinn Fein as "daft" and has warned that he could split the party.
Mr Willie Thompson said: "The proposition by the leader that the UUP should take into government its political opponents, who will then use their position in that government to undermine the Union which is the very reason for the existence of the party, is completely unprecedented and daft.
"Those who support such a proposition must surely be daft themselves. The leader has followed a policy which does not have consensus within the party and he is quite prepared to destroy and split the party to get his own way."
However, a prominent UUP Assembly member, Mr Danny Kennedy, has said he will be supporting Mr Trimble as the Provisional IRA's arms offer represented "some forward movement" on decommissioning.
In a letter to some of his Newry and Armagh constituents, he said: "I believe we have made progress in achieving our twin objectives of devolution and decommissioning. I do not pretend that we have achieved everything to our complete and total satisfaction but the IRA statement does at least represent some forward movement."
The UUP MP, Mr Ken Maginnis, said his party's support for remaining in government with Sinn Fein would depend on progress on decommissioning by the Provisional IRA.
"If they are going to progress through a democratic process as they have signed up to, there must be a sequence of events that will reassure people they are safe in the medium and long term.
"Those who do not fulfil the democratic criteria cannot expect to continue in government ad infinitum." Mr Trimble has not set an actual date for decommissioning in his proposal for tomorrow's meeting but there has been speculation about some element of conditionality.
"In general terms, the UUP is not going to tie its own hands if that can be avoided," Mr Maginnis said. He insisted the inspection of arms dumps was only a "staging post" and he did expect to see actual decommissioning.
SDLP negotiator Mr Sean Farren said there was no chance of the Belfast Agreement being renegotiated if Mr Trimble was defeated tomorrow. He said his party would not respond positively to overtures from anti-agreement unionists and the only alternative would be to proceed on the basis of the Anglo-Irish Agreement.
Meanwhile, UUP support for the Belfast Agreement increased after the Provisional IRA said it would put weapons beyond use, according to a Queen's University/Rowntree Trust opinion poll.
It claims that 72 per cent of UUP supporters want the UUC to vote for a return to Stormont. It puts Protestant support for the Belfast Agreement at 55 per cent, a 6 per cent rise since a previous poll last October.