Ulster Unionist Party (UUP) officials are to meet later today to discuss party policy on the British/Irish joint declaration.
Published in May, the joint declaration outlined plans to reduce British army numbers to 5,000 as part of an attempt to move the peace process forward.
The UUP met three weeks ago to consider proposals for a formal party position on the document, but no vote was taken.
This afternoon a vote is expected on a motion put forward by Mr Trimble.
They will also be examining the continuing disciplinary action against the three rebel MPs who resigned the parliamentary whip over the issue.
Mr Jeffrey Donaldson, who has frequently challenged Mr David Trimble for the party leadership, quit the whip last year over the issue, along with Mr Martin Smyth and Mr David Burnside.