The move came as a US delegation to the province concluded its mission amid rising expectations of a ceasefire announcement by the IRA. The leader of the group, Bruce Morrison, a former congressman who is a confidant of President Bill Clinton, said: 'We are hopeful, based on our discussions, of a dramatic breakthrough.'
Some sources in Belfast said an announcement could come as early as Wednesday. The terms for a suspension of the terrorist campaign are expected to take the form of a statement. The ceasefire may be open-ended and conditional, but that is unlikely to satisfy London or Dublin.
The Government has made it clear there has to be a total cessation of violence by the IRA before its political wing, Sinn Fein, is allowed to take part in negotiations.
Dr John Alderdice, leader of the Alliance Party, said he had no doubt a ceasefire was on the way and added: 'It is just simply a question of what day.'
Unionist feelings were aroused by the leak of documents drawn up by British and Irish officials suggesting that John Major is ready to amend the 1920 Government of Ireland Act, which asserts Westminster's 'supreme authority' over the province, in return for Dublin abandoning its historic claim to Ulster.
The Reverend Ian Paisley, leader of the Democratic Unionist Party, reacted angrily yesterday: 'The Government have gone back on their word to us that there would be no change in the constitutional position of Northern Ireland without the people of Northern Ireland having a referendum to decide that. Now they are tinkering and tampering with the constitutional Act which set up Northern Ireland.'
But the Northern Ireland Office moved quickly to rebut this interpretation, insisting: 'There is no question of any change in the constitutional position of Northern Ireland as part of the UK unless and until that were the wish of a majority of the people of Northern Ireland.
'As the joint declaration made clear, both the British and Irish governments accept this principle of consent and it is central to all the work between them on a joint framework document for political progress.'
The speed with which the NIO acted indicates the sensitivity of relations between London and Dublin in the run-up to the next Anglo-Irish summit, expected in early autumn. Officials have been drawing up a joint understanding that would meet the constitutional requirements of both sides.
The leaked draft documents envisage Parliament amending the 1920 Act to incorporate the principle that there could be a change in the status of Northern Ireland if a majority of its population so wished. In return, Dublin would have to give an unambiguous commitment to hold a referendum on removing Articles Two and Three of its constitution, which lay claim over Northern Ireland. In their place would be an aspiration to a united Ireland.
An NIO spokesman said the 1920 Act was now regarded as largely redundant. 'In terms of its relevance to Northern Ireland it's pretty much a red herring,' he said.
James Molyneaux, leader of the official Unionists, urged calm yesterday, saying: 'With whatever influence I may have in the Unionist family I exhort all strands of that family to refrain from hasty actions.'