Mr David Trimble said last night the British government was making it increasingly difficult for the Ulster Unionists to decide whether to support The Way Forward document aimed at breaking the impasse on decommissioning.
The North's First Minister said uncertainty was deepening, and every time the UUP sought clarification of the latest British-Irish proposals they were left with more questions than answers.
It was announced last night that Mr Blair was cancelling a visit to Poland over the weekend. His spokesman said: "He feels he should be in this country to engage in the discussions on Northern Ireland."
Mr Trimble said his party's worry was that "we make the sacrifice in terms of being prepared to enter into the administration with unreconstructed terrorists.
"But then they refuse to decommission, the automatic failsafe isn't automatic, and we come under pressure by people saying `It's Sinn Fein and they are not the same as the IRA and they are trying and let's not throw this all out'. I don't want to be put in a false position like that."
Mr Trimble said he was in almost constant contact with Downing Street, but had yet to see its proposed legislation or even a draft copy. "I would have expected to have been consulted on it, and it has to be legislated on before next week," he said.
The UUP executive will meet tomorrow to discuss the proposals, but Mr Trimble said he did not think the party could make a judgment until it had more details from Downing Street.
The DUP has said the British government is refusing to guarantee that prisoner releases will be halted and RUC reform stopped as part of its "failsafe" mechanism to reassure unionists on decommissioning if they allow Sinn Fein into an executive.
The party made the claim after meeting the North's Minister of Political Development, Mr Paul Murphy, at Stormont yesterday. The DUP secretary, Mr Nigel Dodds, said: "Paul Murphy couldn't pledge that guarantees on these two matters would be part of the government's legislation to ensure decommissioning."
The DUP deputy leader, Mr Peter Robinson, said unionists could not trust the Provisional IRA. "Nothing the IRA has said to date would indicate that it has any intention of decommissioning." He said the UUP should reject the two governments' The Way Forward document immediately rather than awaiting clarification from Mr Blair.
He could not understand why the party was "hanging around for promises from someone who has deceived them in the past". However, after their meeting with Mr Murphy, a UUP negotiator, Mr Michael McGimpsey, said it was his party's understanding that if the two governments suspended the Belfast Agreement or put it into review, all its provisions including the independent commission on policing and prisoner releases would be affected.
Mr McGimpsey said the UUP had raised several issues with the Minister and was expecting a reply early next week. He criticised the Taoiseach for saying that any executive in the North must be inclusive. He also called for a Provisional IRA statement on decommissioning to help generate confidence.
"While I'm not saying it would be sufficient, certainly it would be helpful if the IRA was to state that it would co-operate with Gen de Chastelain and that we will see decommissioning or even that they support the alleged promises the Sinn Fein leadership made to the two prime ministers last week."
Mr Murphy held separate meetings with the parties yesterday. After its meeting, the Alliance Party urged the UUP to accept The Way Forward document. The party's deputy leader, Mr Seamus Close, said unionists were in a "win-win situation".
"Take your courage in your hands, take the will of the people in your hands, take the desire of the people in your hands and get on with the business," he said.
Meanwhile, Ms Bernadette Sands McKevitt of the 32 County Sovereignty Movement said Mr David Trimble's reluctance to accept the document showed that unionists could not be trusted to treat nationalists fairly in the new government.
"David Trimble is dissatisfied with concessions which hand him the surrender of Provisional IRA weapons. When he refuses concessions of that magnitude and demands more, can anyone seriously suggest that a Stormont administration led by him would be a springboard to equality, justice and a united Ireland?" she said.
The US Congressman, Mr Peter King, who is visiting the North, said he believed the Provisional IRA was ready to hand over weapons. If Mr Trimble did not accept The Way Forward many people would hold him responsible for stalling the peace process, Mr King added.