Hardline anti-Belfast Agreement MP Jeffrey Donaldson tonight faced calls not to walk away from the troubled Ulster Unionists and trigger a split which could wreck the party.
Close associates urged him to stay on and intensify his opposition to David Trimble's leadership and continued support for the Good Friday Agreement.
South Antrim MP David Burnside was among those who called on him not to quit.
He said: "It would be a tactical mistake now when the pressure has been building on the leadership for Jeffrey and others to walk away now."
The two MPs are to have more talks in London tomorrow to see if they can develop a strategy aimed at maintaining internal pressure on Mr Trimble.
However, other colleagues of Mr Donaldson believe his position would be significantly weakened if he stayed on in the party after hinting strongly that he had enough.
Either way the UUP, with 56 per cent backing Mr Trimble at a crucial council meeting last night and 44 per cent behind Mr Donaldson, is in the middle of its biggest crisis for 30 years.
Mr Donaldson is considering his next move which includes an invitation to join the Rev Ian Paisley's Democratic Unionist Party.
The pressure on him to remain is intense but he is also examining the possibility of leading disaffected members of the party into a coalition against the Agreement with the DUP.
Mr Burnside insisted the anti-Agreement wing of the party had succeeded in toughening Mr Trimble's line on sharing power with Sinn Fein in any new devolved administration.
"The feeling on the ground right now among the unionist people is that they do not want any more unionist parties to be set up.
"My advice to Jeffrey and others is to get the Ulster Unionist Party right and then negotiate with other unionist parties, including the DUP, a united coalition which can negotiate a better agreement."
The divisions within the UUP are the latest in a series of blows suffered by the peace process since the collapse of devolution last October.
Sinn Fein's Mr Martin McGuinness urged Mr Trimble to adopt a more positive approach to the full implementation of the Good Friday Agreement.
"The whole focus today is where does Jeffrey Donaldson go from here - that is not where my focus is," the Mid Ulster MP said.
"My focus is where does the British Prime Minister go from here, where does David Trimble go from here?
"What I want to see is them defending and fully implementing the Good Friday Agreement."
SDLP leader Mr Mark Durkan also said Mr Trimble needed to be clearer about his views on the Agreement.
"Too many people don't know whether the UUP are up for all of the Agreement offers this community," the former Deputy First Minister argued.
"Equally too many people don't know whether the republican movement are up to the standards and commitments that the Agreement requires.
"It is now time to move beyond all the speculating and speculation about the disarray within the UUP and move to consolidate a pro-Agreement axis right across the different parties that claim to be pro-Agreement."
PA