Senior UUP sources have confirmed that "a major effort" is under way to ensure a direct challenge to Mr David Trimble's leadership at the party's annual meeting on Saturday week.
The indications suggest a "stalking horse" challenger, with a Craigavon councillor, Mr Jonathan Bell, among a number of people being canvassed behind the scenes.
However, there is speculation that Mr Trimble might face a "mainstream" opponent, with attention focused on the East Derry MP, Mr William Ross.
One leading anti-agreement campaigner told The Irish Times he had no knowledge of this, and thought it highly unlikely that the challenge, which he fully expected, would come from within the parliamentary party.
However, friends of Mr Ross suggested nothing could be ruled in or out at this stage, with one adding: "It is time for thinking unionists to ask where Mr Trimble is taking them, if he now has a policy, and whether he can rally the party to meet the electoral challenges of the year ahead."
Meanwhile, a second threat to Mr Trimble surfaced, with a revived attempt by Mr David Burnside, the London-based businessman, to have the party demand the restoration of the RUC's royal title as a condition of resuming membership of the suspended Northern Ireland Executive.
It is understood party officers are staging a desperate attempt to persuade Mr Burnside to drop or amend his motion. However, supporters of the campaign to "save the RUC" say Mr Burnside is likely to seek an emergency meeting of the Ulster Unionist Council if his motion is not accepted for debate at the a.g.m. on March 25th.
There were unconfirmed reports at the weekend that Mr Burnside's RUC campaign has the support of Mr John Taylor, the UUP's deputy leader. Party sources also said Mr Taylor had told a policy review committee last week that the Ulster Unionists should start distancing themselves from the Belfast Agreement, which in his view had failed.
One supporter of Mr Trimble last night said a stalking-horse challenge would mean nothing, in that it would "only confirm what we all know, namely that a lot of people are opposed to Trimble."
He said the situation was not the same as that which saw a Queen's University student, Mr Lee Reynolds, challenge Mr James Molyneaux in 1995. In that case Mr Reynolds's 15 per cent share of the vote proved enough to destabilise a leadership which had previously been unchallenged.