We appreciate the there are difficulties within unionism and understand the destabilising effect of all of these allegations.

Sinn Fein's Gerry Adams

At a news conference after the meeting, Mr Trimble appeared sombre and said he had cut off the Sinn Fein politicians' repeated denials of IRA involvement.

He went on: "We cut that short and told them that wasn't the point.

"We didn't engage in a discussion on who did what to whom.

"The crucial point was explained that outside, nobody in the unionist community believed a word that republicans are saying about recent events - nobody."

"This is rapidly draining the credibility of this administration and this process."

Mr Trimble, who during the three years of the powersharing arrangement has applied sanctions against Sinn Fein's ministers on a number of occasions, said that this time he did not "make any threats" and issued no ultimatums.

"But we said that against the background of the situation, it is simply not going to be possible to sustain this process unless republicans can restore their credibility," he said.

'No crisis'

Gerry Adams said the meeting was "not a showdown".

And he said there was "bewilderment" in the nationalist and republican community that "at a time when the process should be calmly moving on after the enormous move by the IRA on the weapons issue that we are in this crisis".

UUP MP Jeffrey Donaldson: "Sinn Fein's position is untenable"

Referring to the allegations about IRA activity, Mr Adams said: "There are difficulties within republicanism about these events and about how others have reacted to the these events.

"And as Mr Trimble has told us, there are difficulties within unionism.

"And we appreciate that this is the case and understand the destabilising effect of all of these allegations.

"But the destabilising is more acute within unionism."

Mr Adams had refused to attend the US Congress's hearing into allegations about the IRA's links with Colombia, on Wednesday.

However, republicans believe the Washington hearing has done far less damage to their cause than some had predicted.

Meanwhile, Ulster Unionist MP Jeffrey Donaldson, who did not attend the meeting, said the talks between his party leader and Mr Adams would mean nothing if it was not backed up by full IRA weapons decommissioning.

He said: "In my opinion Sinn Fein's position of having two ministers in the government of Northern Ireland and the IRA continuing to engage in acts of terrorism are incompatible and therefore Sinn Fein's position is untenable."