The sources were speaking after a five-hour meeting of the DUP's 120-strong ruling executive, one of the most important gatherings in the party's history.

Negotiations were continuing with the British government late last night, and party leader Ian Paisley was said to be in direct telephone contact with Tony Blair.

The two governments have given the DUP until tomorrow to agree to form a government with Sinn Fein.

Ministerial nominations are due to take place tomorrow with the new Executive to meet on Tuesday.

Those at the executive meeting were under strict instructions not to speak to the press.

However, one DUP source said: "Monday is not going to happen. There will be no nominations of ministers by us.

But May is looking a distinct possibility."

London has said that if tomorrow's deadline isn't met, the Assembly will be closed down, Assembly members' salaries will be stopped, and water bills will be sent to the public on Tuesday.

It remains to be seen whether the British government will end the entire Stormont project, as an Executive formed in May would still allow Blair to leave office claiming he had brought peace to Ireland.

The DUP was due to issue a resolution last night detailing its plans for power-sharing and the requirements that it felt Sinn Fein and the British government still had to meet.

Sources said it would be "a substantial announcement".

DUP sources believe that, despite Blair's threats, the British government will "do some fancy footwork" to give the party time for a May deal.

A DUP spokesman described yesterday's executive meeting as "good and constructive". The DUP still has concerns about Sinn Fein's attitude to the Police Service of Northern Ireland (PSNI). It also wants London to agree an exclusion mechanism whereby Sinn Fein could be thrown out of government if the IRA "misbehaves", allowing the power-sharing administration to continue without Sinn Fein.