Dissident Ulster Unionist MP Mr Jeffrey Donaldson seems likely to seek further "clarification" about Mr Tony Blair's plans for legislation giving effect to the Belfast Agreement before finally committing to the Yes or No campaigns in next week's referendum.
In his eagerly awaited speech in Belfast last night, the British Prime Minister declared "there can be no fudge between democracy and terror".
Speaking at the King's Hall, Mr Blair said: "People want to know that if these parties (republican and loyalist) are going to benefit from proposals in the agreement such as accelerated prisoner releases and ministerial posts, their commitment to democratic, non-violent means must be established in an objective, meaningful and verifiable way. Those who have used the twin tactics of ballot box and the gun must make a clear choice."
In a direct attempt to address growing unionist opposition to the agreement, Mr Blair spelt out four tough tests to ensure that "the terms and the spirit" of the agreement would be met. Those tests would "provide evidence upon which to base an overall judgement - a judgement which will necessarily become more rigorous over time."
And the Prime Minister said he had decided "that they must be given legislative expression directly and plainly in the legislation to come before parliament in the coming weeks and months."
The Ulster Unionist Party leader, Mr David Trimble, immediately welcomed Mr Blair's speech and the promise of "plain and direct legislation linking prisoner releases and [taking] office [in the planned Northern Ireland executive] to a permanent end to violence and decommissioning."
Welcoming the Taoiseach's earlier call on the IRA to declare that its "war" was at an end, Mr Trimble said Mr Blair's speech was the result of four months of effort "to ensure strong legislation to underpin all that we have achieved."
However, Mr Blair's attempt to persuade Mr Donaldson back into the Trimble fold certainly won no immediate reward. The Lagan Valley MP told Channel 4 News that he had not had time to study the speech and wanted to reflect and consider it with colleagues.
But he appeared to be sticking to his previously declared requirement of "actual and ongoing decommissioning" before Sinn Fein could take its place in the new political structures. He said Mr Blair had "made an effort" to address unionist concerns but he wanted "to be sure that what the Prime Minister has said is for real."
Mr Donaldson's discussions with colleagues were continuing late into the night, amid suggestions that he might seek a further meeting with Mr Blair, so delaying a final decision into next week.
Some of those close to Mr Donaldson were indicating concern that Mr Blair had not defined a time scale for decommissioning, or addressed whether he envisaged Sinn Fein entering the executive after the assembly elections. The suggestion again surfaced that the formation of the executive might be delayed until power is transferred to the assembly, so unionists could see and test the proposed legislation.
Mr Blair's factors to be considered in determining if the spirit and terms of the agreement were being met included an unequivocal commitment "that there is an end to violence for good"; the "progressive abandonment and dismantling of paramilitary structures"; full co-operation with the independent commission on decommissioning; and "no other organisations being deliberately used as proxies for violence."