DUP sources have said "robust exchanges" are expected at internal meetings over coming weeks to decide the party's response to Sinn Féin's offer of a special ard fheis on policing.
Party sources said they feared Ian Paisley had told Tony Blair that the 26 March deadline for establishing a power-sharing executive was still possible.
"Policy agreed by the DUP executive, our party's ruling body, means no such promises are possible, " one source said.
DUP figures such as Jim Allister and Willie McCrea believe the 26 March deadline is impossible and must be rejected.
McCrea told the Sunday Tribune that Gerry Adams and Martin McGuinness should be put on trial like Saddam Hussein, not put into government.
"Saddam's trial is a reminder that those guilty of crimes against humanity should be toppled rather than elevated to high office, " he said.
Strong opposition to governing with Sinn Féin is likely to be aired at the meetings. The DUP's 19-strong officer team meets this week. The party's Assembly group will then gather, as will its 110-strong executive.
McCrea said: "Unless Adams and McGuinness turn into magicians, I don't see how we can have all we need delivered by 26 March. IRA structures must be dismantled, their ill-gotten criminal gains handed over, information passed to police on Robert McCartney's murderers, and details disclosed of the location of the bodies of the disappeared. We also must be convinced by future IMC reports and reports from our own security sources."
Meanwhile, anti-agreement republicans are to discuss standing candidates to challenge Sinn Féin in the assembly elections.
The 'Concerned Republicans' group, which has organised meetings on policing across the North and includes former Sinn Féin members, the IRSP, the 32-County Sovereignty Movement, and unaligned republicans, opposes the St Andrew's agreement and Sinn Féin signing up to policing.
Marion Price of the Sovereignty Movement said: "Sinn Féin is vulnerable in some seats and people are aware of that. People are debating the possibility of running candidates and I wouldn't be opposed to that."
Laurence O'Neill, a veteran Sinn Féin member who resigned from the party recently, has been mentioned as a candidate.
