The North's First Minister, Mr David Trimble, has came under strong pressure from anti-agreement unionists to expel Sinn Fein from the administration following the killing in west Belfast of a "Real IRA" member, Mr Joe O'Connor.
In an attempt to avert the growing crisis in the peace process, the Minister for Foreign Affairs, Mr Cowen, and the Northern Secretary, Mr Peter Mandelson, met in Belfast last night.
Neither man would comment as they arrived at Stormont to discuss decommissioning and police reform.
In the Assembly, the DUP demanded that Mr Trimble take action against Sinn Fein following the O'Connor killing.
No group has admitted responsibility but local people and the victim's family claim the Provisional IRA was involved. Sinn Fein has denied this claim.
Mr Ian Paisley jnr said the Provisional IRA had been involved in three recent murders and an arms smuggling operation in Florida.
In the Assembly he asked: "Instead of expressing disappointment, what sanctions is he [David Trimble] going to put on the Provisional IRA and their Ministers in government?"
Mr Trimble replied that unlike the DUP, he was careful not to deploy "hyperbole, exaggeration and bombast" about claims of Provisional IRA involvement, and was awaiting a statement from the RUC Chief Constable, Sir Ronnie Flanagan, on possible Provisional involvement.
"I hope the Chief Constable will quickly be in a position to indicate what the police view is as to who is responsible for this and other murders. We shouldn't jump to conclusions that serve one political party's purpose rather than others.
"We need to have a balanced view from the Chief Constable in order to arrive at a conclusion."
The Northern Ireland Unionist Party leader, Mr Cedric Wilson, said Mr Trimble must guarantee that he would take action against Sinn Fein if Provisional IRA involvement was confirmed.
"Would he give an undertaking to remove Sinn Fein representatives from the Executive and, failing that, will he give an undertaking that he will do the honourable and decent thing and lead his party out of the Executive?" he asked.
Meanwhile the Enterprise Minister, Sir Reg Empey of the UUP, said doubts remained over the commitment of paramilitary groups to the peace process. He said recent violence was undermining the Belfast Agreement.
He criticised Sinn Fein's statement last weekend that the Provisional IRA would honour its commitment to put weapons beyond use but would not be "shoehorned" by unionists into doing so.
He accused Sinn Fein of using the arms inspections as "leverage" to obtain more concessions from the British government.
His party, he said, was trying to advance the peace process but could not do so alone.
"We are not getting reciprocation from people in possession of weapons. They are cocking a snook at the entire community. They are continuing to involve themselves in racketeering, smuggling and all sorts of other activities."