The Ulster Unionist party leader, Mr David Trimble, may seek a review of the Belfast Agreement should Sinn Fein be offered seats on an executive before IRA decommissioning, informed party sources have said.
The First Minister is said to be receiving legal advice and preparing a challenge should the Northern Secretary, Dr Mo Mowlam, set the mechanism in motion that would grant Sinn Fein ministerial positions before an arms handover.
The request for a review is expected to be made under the provision for a review in Strand 1, paragraph 36, of the agreement which allows for the political parties in the North signed up to the document to meet and review the document.
A source close to Mr Trimble said last night this was the "most appropriate" mechanism being considered.
Any request for a review will come when the deadline for devolution has passed. According to a spokesman for Mr Trimble the agreement contains two provisions for review, providing the First Minister with "a lot of tactical options".
The favoured outcome of a review for Mr Trimble would be the alteration of the section of the document addressing the d'Hondt automatic allocation of ministerial positions and the exclusion of Sinn Fein from the executive until decommissioning takes place.
However, the Deputy First Minister, Mr Seamus Mallon, said yesterday that round-table negotiations by the parties did not amount to a review of the agreement. He said such discussions could take place at any time but did not rank as a review of the document.
A "formal" review must include the British and Irish governments, he said.
A second provision for a review comes in the review section, paragraph 4 of the document, which allows for a review under an independent chairman or the involvement of the governments.
Sources close to Mr Trimble said a request for a review by the First Minister did not need sanction by the Deputy First Minister and that, as yet, both provisions in the agreement for a review were being considered.
According to Mr Mallon, a review of the Belfast Agreement would be "premature" at this stage of the implementation process.
Speaking after an engagement in Armagh he encouraged the setting up of the institutions and arrangements outlined in the agreement and said people should be "put in place", poised to assume ministerial office for the devolution of power in March.
He also urged Mr Trimble to work the agreement. "Let's get on, set up the institutions, do everything that we have to do under that agreement."
Mr Mallon pledged not to break the agreement's key element of "inclusivity" and enter an executive without Sinn Fein. "We are not going to break our word," he said.
Meanwhile, plans are being finalised for a joint trip by the First and Deputy First Ministers to Brussels and Bonn with a possible departure date of February 7th. Mr Trimble and Mr Mallon are scheduled to meet the German Chancellor, Mr Gerhardt Schroder and the German Finance Minister, Mr Oskar Lafontaine.