Mr Gerry Adams will lead a Sinn Fein delegation into "urgent" talks with the British Prime Minister, Mr Tony Blair, at Downing Street this afternoon.
Number 10 insisted last night that the meeting was scheduled last week and had not been hastily arranged following Mr Martin McGuinness's weekend rejection of the proposed heads of agreement tabled by the British and Irish governments to the Stormont talks process last Monday.
Mr McGuinness repeated again yesterday that Sinn Fein would remain in the talks process, but he insisted that the party would not negotiate on the basis of the joint British-Irish propositions. Speaking on the BBC's On The Record programme, Mr McGuinness said that the proposals had "gone down very badly" within Sinn Fein and also within the wider nationalist community. Sinn Fein, he said, would be returning to the talks "to challenge what we believe is a very serious mistake".
Today's meeting will be the party's third with Mr Blair and the Northern Ireland Secretary, Dr Mo Mowlam, and it comes less than six weeks after their first ground-breaking encounter at Number 10. The Prime Minister's spokesman said: "It (the meeting) should be seen as part of the ongoing discussions between the prime minister and those involved in the talks process. They agreed the last time they met that, provided there continued to be a further commitment exclusively to peaceful methods, there would be a further meeting in the new year."
A Sinn Fein spokesman, confirming that the meeting had been sought a week ago, said: "Mr Adams made it clear that nationalist and republican opinion would see the strategy being suggested as a retreat from the previously-stated positions of the two governments, and in response to unionist tactics and loyalist killings".
In advance of the parties resuming their talks at Stormont, the Sinn Fein spokesman said that the basis for negotiation needed to be "a bridge to the future, not a Uturn to the past".
Earlier, Mr McGuinness, in a number of media interviews, insisted that the British-Irish blueprint could not form the basis for negotiation. While Sinn Fein would attend the talks, which resume this morning, they would be at Stormont to oppose the heads of agreement.
Mr McGuinness said that there could be no internal settlement and accused the British and Irish governments of succumbing to the "Orange card" of loyalist violence. "These propositions were presented to the talks table from the barrel of unionist and loyalist guns", he added.
The DUP took a different view of the British-Irish proposals. The party leader, the Rev Ian Paisley, described them as "the Framework Document revisited" and insisted that they offered the Republic an executive role in the running of Northern Ireland.
The Ulster Unionist Party leader, Mr David Trimble, had what he described as a "positive" meeting with 60 of the UUP's senior councillors at the weekend. Mr Trimble briefed his party members on the British-Irish document and gave them an update on the talks process.
The Taoiseach denied that the Framework Document had been diluted by the two governments in response to unionist threats and loyalist killings. Mr Ahern sought to reassure nationalists and republicans that all aspects of the Framework Document could be discussed in the negotiations between the political parties.