Dr Mo Mowlam will this week formally invite Sinn Fein to join all-party negotiations on the future of Northern Ireland. The Secretary of State will deliver her verdict on the "quality" of the IRA ceasefire on Thursday or Friday - six weeks after the reinstatement of the 1994 cessation.
Her decision, based on the advice of security chiefs, will pave the way for a historic meeting between the British Prime Minister, Mr Tony Blair, and the Sinn Fein president, Mr Gerry Adams.
While Downing Street yesterday maintained there were no plans for such a meeting at this stage, the face-to-face encounter was promised by British officials to Sinn Fein's Mr Martin McGuinness before the IRA's July ceasefire announcement. Mr McGuinness was told explicitly that meetings with Mr Blair "would be dealt with on the same basis as for other participants" once Sinn Fein had joined the negotiations.
Despite weekend speculation to the contrary, the meeting between Mr Blair and Mr Adams - when it comes - will almost certainly take place in 10 Downing Street. Sinn Fein yesterday expressed confidence that it would take place within weeks.
Before then Sinn Fein will be invited to a formal plenary session of the Stormont talks, scheduled for September 9th, at which the party will be required to sign up to the Mitchell principles of democracy and non-violence. Despite ministers' belief that Ulster Unionist participation is still "in the balance", Mr Blair and Dr Mowlam are determined that substantive negotiations about a political settlement will begin on September 15th.
Irish Government sources are confident that, after initial difficulties, the Ulster Unionists will sit down in round-table negotiations with Sinn Fein. However, the current British assessment of the chances of that happening, at least at an early stage in the process, is put at "fifty-fifty".
Mr David Trimble, the UUP leader, will lead an intensive consultation exercise within his party, and among the wider pro-Union community, in the coming weeks. However, senior sources say he is likely to opt for a process of bilateral and multilateral talks, by which the UUP would sustain the existing talks process without dealing directly with Sinn Fein. The Democratic Unionists have already called for an alternative to the present talks format. But the UUP leader wants to maintain his "leverage" under the existing ground rules, which require "sufficient consensus" for any matter to be agreed.
Potentially crucial to the UUP's attitude will be decisions London hopes can be taken this week about the chairmanship and composition of the proposed independent commission to address the question of decommissioning paramilitary weapons alongside political negotiations.
Dr Mowlam will meet the Minister for Foreign Affairs, Mr Burke, in Belfast tomorrow amid reports that Dublin is resisting the appointment of Gen John de Chastelain as chairman of the Commission.
British sources were last night unable to confirm that the general would be appointed, while maintaining their hopes that the commission, with key personnel at least, would be in place before September 15th.