Putting himself directly at odds with Douglas Hurd, the Foreign Secretary, the Irish premier, Albert Reynolds, told a press conference in Brussels: 'A minimum communique saying nothing would not contribute to an end of violence. If I consider it to be anodyne I will not be signing.'
With a joint declaration thought possible this week, Mr Reynolds's comments seemed calculated to put more pressure on Mr Major to make concessions on areas of outstanding disagreement.
The Taoiseach also took Downing Street by surprise by announcing that the two leaders may have two meetings this week, instead of the expected one, before a declaration.
Officials will continue working throughout the weekend, and the two prime ministers are to review progress by telephone tomorrow. Although he would like a conclusion before Christmas, Mr Reynolds said he would attend as many meetings as it took to clinch a deal.
Mr Major declined to be drawn into the diplomatic exchanges, but a British source said: 'We are aiming for a serious and balanced text and progress has, and is, being made. We are not going to be put off our objectives.'
Mr Reynolds's high-risk diplomacy is being seen as a late attempt to extract movement from the British over crucial issues. One Irish source said that Mr Reynolds 'will only sign what, in his judgement, stands a reasonable or good chance of delivering Sinn Fein'.
The Irish believe that, in several key respects, the proposed deal on the table does not satisfy that criterion. Outstanding problems include the vexed issue of a joint declaration of the Irish people's right to determine their future, based on consent. Mr Reynolds himself emphasised the need for a balanced initiative so that neither of the two communities felt 'hard done by'.
His call for a substantial peace declaration was in sharp contrast to the position taken by Mr Hurd, who indicated that the declaration would not necessarily end the violence. He told Radio 4's Today prgramme that he hoped the two governments would produce a declaration that 'will influence the men of violence, the murderers'. But he added: 'One can't be sure of that but in any case there is advantage in it in bringing together, updating as it were, what the two governments, what the men of peace if you like, actually believe in and how they see the future.'
The peace process was complicated last night by claims in the Mail on Sunday that the Dublin government has been in contact with the loyalist paramilitaries for several months. John Taylor, Unionist MP for Strangford, said he and his colleagues had been working on the assumption that Dublin was in contact with the Ulster Volunteer Force.
Several areas of difficulty remain between the two governments. The Irish envisage a declaration including a reference to self-determination which would lead to a constitutional conference of all political parties in the North, including Sinn Fein. That would proceed towards referendums on an agreed process in the North and the South, with the British endorsing a 'yes' vote. In return, the Irish would bring forward a referendum on the repeal of articles two and three of their constitution, which stake a claim to the North.
Apart from the difficulties of exacerbating Unionist fears by use of such terms as 'self-determination', Britain is hostile to the referendum process. That is because of Unionist fears that the result of two referendums would be aggregrated, thereby creating a natural nationalist majority.
Ken Maginnis, Ulster Unionist MP for Fermanagh and South Tyrone, said: 'I see the Irish holding out for something which is impossible, something that will not bring peace.'