Mr David Trimble is facing a critical meeting of his Ulster Unionist Party ruling executive in Belfast today in what some of his supporters are convinced is the prelude to a challenge to his leadership of the party.
Two leading anti-Belfast Agreement Ulster Unionists, Mr David Burnside and Mr Jeffrey Donaldson, went public yesterday in demanding that sanctions be imposed if the British Prime Minister, Mr Tony Blair, fails to take action against Sinn Féin.
Mr Trimble, after travelling from Jersey to Belfast, last night met senior party members to discuss what strategy to employ today to resist the mounting pressure from the sceptical wing of his party.
A motion in the name of Mr Donaldson, supported by Mr Burnside, is understood to be down for today's meeting of the 110-member executive.
It proposes that the party initiate a ministerial withdrawal from the Northern Executive on July 1st if Sinn Féin is not penalised by the British government for issues such as Colombia, Castlereagh and the continuing street disturbances, according to unionist sources.
The problem for Mr Trimble is that all strands of unionism from pro-agreement to anti-agreement are angered by what they believe is republican involvement in Colombia, in the raid on the police Special Branch office at Castlereagh station, and in fomenting the street violence in Belfast.
Mr Trimble was last night weighing up whether to pre-empt the Donaldson-Burnside initiative by proposing his own set of sanctions against Sinn Féin, or whether to insist that he alone as leader must have the freedom to determine how these issues are addressed, sources said.
The gravity of the situation was illustrated by Mr Trimble's decision to demand a meeting with Mr Blair at Jersey airport yesterday morning, where the British Prime Minister was holding a bilateral meeting with the Taoiseach, Mr Ahern.
Mr Trimble confronted Mr Blair on the problems facing unionism and his leadership, it is understood.
They also travelled together in Mr Blair's car from the airport to a meeting of the British-Irish Council, where a stony-faced Mr Trimble could be seen in solemn discussion with the Prime Minister.
Mr Blair at a joint press conference with Mr Ahern said he understood unionist concerns. "We are considering how we address these issues and the anxieties that unionists have," he said, without stating what action, if any, he might take to help ease unionist worries.
Unionist sources say that the Donaldson-Burnside wing of the party has the requisite 60 signatories to call another Ulster Unionist Council. But whether it would directly challenge his leadership is still unclear.
Mr Trimble was said to be in combative mood last night, fully prepared to defend his stewardship of the Ulster Unionist Party.
Mr Donaldson and Mr Burnside were equally assertive, although neither characterised today's executive meeting as the precursor to a heave against the First Minister. Mr Donaldson said he was in no doubt the party was facing a "defining moment", and that the UUP's credibility was "on the line".
"Somebody has to face up to the charge that the IRA has not bought into a peace process. Government doesn't seem willing to do anything about it. So the time has come where the party must act to protect the democratic process," he added.
Mr Burnside said the Ulster Unionist Assembly party should seek the expulsion of Mr Martin McGuinness and Ms Bairbre de Brun from the executive.