President Clinton's meeting with the British Prime Minister tonight is now seen by the Government as crucial to breaking the peace process deadlock before Christmas.
The US President is expected to press Mr Blair to consider a major British gesture of demilitarisation in south Armagh, seen by Dublin as the key to a substantial IRA move on decommissioning.
He will also press the IRA - through discussions with Sinn Fein in Belfast this morning - to agree to a sustained involvement in talks with the de Chastelain commission leading towards real movement on putting weapons beyond use.
Mr Clinton arrived in Belfast last night after addressing thousands of people at an open-air rally in Dundalk. The Taoiseach told him that while many people had been involved in the peace process, "it would not have been possible without you".
After a day spent largely celebrating Mr Clinton's peace process role and promoting economic links between Ireland and the US, President Clinton and his officials will be focused on hard politics today.
In a round of talks with the North's party leaders in Belfast this morning, Mr Clinton will encourage them to use the current intensive discussions to break the deadlock. He will then make what is expected to be his keynote political speech at Belfast's new Odyssey Centre before travelling with Mr Blair to Chequers for their crucial talks.
Government sources confirmed last night there was still a major effort under way to achieve success before Christmas, but they would give no indication of how optimistic they were of success.
The republican position is that they will make a significant move only in the context of a major reduction in the visible British security presence in the republican stronghold of south Armagh. However, the British security forces' advice is that further demilitarisation will play into the hands of republican dissidents.
During 30 minutes of talks at Government Buildings yesterday the Taoiseach, according to a Government spokesman, "asked President Clinton to encourage all sides to stretch further and to take advantage of the current dialogue in order to reach a resolution".
This is what he will do this morning with the North's main party leaders, before being joined in Belfast later this afternoon by Mr Blair. The formula being worked on at senior level involves a substantial British gesture - or firm commitment to such a gesture - on demilitarisation in south Armagh. This may involve the dismantling of lookout towers or military bases, or a significant further troop reduction.
The IRA in turn would commit itself to a process of engagement with the international decommissioning body to discuss precise ways to put weapons beyond use. One of several options under consideration is the concreting over of certain weapons dumps. Gen de Chastelain would be asked to vouch for the credibility of such IRA engagement.
The third part of the deal would be the ending by the North's First Minister Mr David Trimble of his vetoing of Sinn Fein Ministers' attendance at meetings of the North-South Ministerial Council.
Mr Clinton had dinner with the British Prime Minister, Mr. Tony Blair, in the Belfast Hilton Hotel last night. Mr Blair arrived by helicopter in Belfast shortly after 10 p.m., 12 hours earlier than his scheduled arrival this morning.