Unity within the Ulster Unionists is again under threat as the party attempts to bring a rebel MP to heel.

Senior UUP members were set to meet on Friday at an executive meeting to decide whether to take further action against its MP Jeffrey Donaldson.

The Lagan Valley MP had renewed his criticism of party leader David Trimble and warned he will work closely with the rival DUP to fight the Good Friday Agreement.

During last month's elections for the Belfast Assembly, Donaldson launched his own mini-manifesto and made repeated calls for a change in his party's leadership.

Donaldson claimed the tide had turned against the Agreement.

"I intend to use the mandate I have been given to work with the Democratic Unionist Party, and with other unionists, to achieve the change the unionist people voted for," he said.

Party leader David Trimble has seen off renewed resignation threats, but party hardliners believe his position is now untenable.

The UUP will either make a new call for him to come back into line or take "decisive action". "There have been lots of complaints and patience has run out among some people," said a spokesman.

Whilst negotiations on the Good Friday Agreement have been put on hold, British ministers are expected to mount a fresh push in the New Year.

Tony Blair is expected to meet with senior DUP figures before Christmas to stress the need for constructive dialogue.

But hardline unionists including Donaldson will press for a wholesale renegotiation of the agreement.

The Lagan Valley MP and assembly member is no stranger to fights with his party, having been suspended along with two other MPs for defying the leadership.

He took the party to the High Court to have the order overturned. Donaldson has an invitation to join the DUP - a possibility he has not ruled out.

A statement is expected to be issued later today.