Sinn Féin president Mr Gerry Adams will today tell a senior US Government official the Democratic Unionist Party is blocking a return to power sharing in Northern Ireland.
The West Belfast MP will hold talks in Washington with US President George Bush's special envoy to Northern Ireland, Ambassador Mitchell Reiss.
The meeting will take place as government officials from Dublin and London work on a formula to revive devolution.
But as Mr Adams prepared for today's discussion, his colleague Mr Martin McGuinness claimed the Rev Ian Paisley's DUP was feeling the pressure as other parties realised it was the main obstacle to political progress.
Noting DUP criticism of the Taoiseach, Mr McGuinness said: "Ian Paisley's comments are a clear response to the criticism from the Taoiseach of the approach of the DUP.
"It is also something to do with the fact that Ian Paisley knows that the [British] government is going to call the situation soon and it may call it in a way that will acutely embarrass the DUP.
"After last November's Assembly election, the DUP was very keen to present itself as a new, confident leadership.
"However I and others in this process have seen little sign of any leadership or confidence from the DUP in their handling of this situation."
British and Irish officials believe the IRA could undertake significant moves on disarmament and paramilitary activity if there is a comprehensive deal to revive the Assembly and implement the Belfast Agreement.
However those moves have been put on hold because of a dispute between the DUP and nationalists over future power sharing arrangements.
The DUP has been pressing for changes to the way the First and Deputy First Ministers are elected in the Assembly.
This has been opposed by Sinn Féin and the nationalist SDLP who have also accused the Rev Paisley's party of trying to secure a veto over the work of other parties' devolved ministers. Nationalists have also hit out at the DUP's approach to cross border co-operation with the Government, accusing them of trying to dilute it and limit the scope of it.
The Rev Paisley insisted last night his party would not be signing up to a rag bag of a deal and he accused the Taoiseach, Mr Ahern of acting in bad faith in recent remarks about the deadlock in the process.
On Tuesday, Mr hinted a proposal from the IRA to fully disarm by the end of this year was on the negotiating table. He also suggested a deal was tantalisingly close and it would be a terrible tragedy if parties did not sign up to it for tactical reasons.
Mr Paisley responded: "It is outrageous that Bertie Ahern is now in the business of lecturing unionists to admit Sinn Fein/IRA into the government of Northern Ireland at a time when its own party refuses to countenance Sinn Fein in power in the Republic."
"His comments indicate bad faith to the democratic community in circumstances where the Independent Monitoring Commission has indicated that the IRA is still engaged in all of the activities that both Mr Ahern and Mr Blair believed were at an end in October of last year," he said.