The British Prime Minister, Mr Tony Blair, and the Ulster Unionist leader, Mr David Trimble, suffered a setback last night as the Ulster Unionist MP, Mr Jeffrey Donaldson, confirmed he will be voting No in next Friday's referendum on the Belfast Agreement.
Mr Donaldson's decision, which appeared to come as a surprise to 10 Downing Street, gave a further boost to the No campaign already cheered by polling evidence suggesting that a majority of unionists are set to vote against the agreement.
Meanwhile, the Loyalist Volunteer Force, the dissident paramilitary group formerly led by Billy Wright, has announced a ceasefire to encourage a No vote in the referendum.
The US President, Mr Clinton, and Mr Blair are expected to issue a joint appeal for a Yes vote tomorrow. In Birmingham for the G8 summit last night, Mr Clinton said: "To me, as a friend from the outside, the referendum appears to be a chance for a generation for peace."
In a statement Mr Donaldson and six party colleagues, including several members of Mr Trimble's original multi-party talks team, rejected the Prime Minister's assurance of tough legislative tests governing the conditions for proposed prisoner releases and Sinn Fein's eligibility to serve n the Northern Ireland executive.
In a series of telephone calls during the day Mr Blair and his officials attempted to persuade Mr Donaldson to keep his options open. But Mr Donaldson and his colleagues said that on the basis of their present assessment and in the absence of their concerns being fully addressed "we continue to be of the view that we cannot in conscience recommend this agreement to the people of Northern Ireland".
While this stopped short of explicit advice to the unionist electorate to vote No, he later confirmed that he would be doing so.
Mr Trimble said he was "saddened that Jeffrey has not been able to accept the Prime Minister's assurances". It was the UUP leader's view that Mr Blair's speech on Thursday night had "answered all the concerns expressed by Jeffrey and his colleagues".
"The RUC will not be disbanded; only prisoners linked to paramilitary groups observing a ceasefire will be released, and then only on licence; and the requirement to decommission before taking executive posts will be under pinned by legislation and so given the force of law," he said.
But Mr Donaldson and his colleagues, while welcoming "the positive sentiments expressed in the speech" maintained "there are a number of ambiguities and omis sions which cause us continuing concern."
Their statement said: "The position of the Prime Minister appears to be that the terms of the agreement are unalterable, and it therefore remains to be seen whether this permits him to include the necessary, effective safeguards which need to be inserted into the legislation."
The seven said their concerns included:
an inadequate reassurance on the future of the RUC.
no clear requirement to decommission before holding ministerial office.
the absence of clear measures to exclude from office those who fail to honour the commitment to non-violence and exclusively peaceful means beyond the cross-community vote proposed in the Agreement.
the absence of clearly defined linkages between the need for the commencement of actual and ongoing decommissioning and the release of prisoners.
the absence of any provisions to exclude from office in the shadow assembly those still committed to the twin approach of ballot-box and gun.