Taoiseach Bertie Ahern is to meet British Prime Minister Tony Blair for talks on Northern Ireland and the European Constitution at Downing Street on Wednesday.
Mr Ahern is also to hold separate talks with a DUP delegation led by party leader the Rev Ian Paisley, at the Irish Embassy.
The meeting will focus very heavily on the current crisis relating to the European Constitution, in advance of the European Summit the following day.
With Britain to take over the presidency of the EU from next month talks will also focus on the EU budget for the five years from 2007.
In relation to Northern Ireland Number 10 is describing Wednesday's meeting with the Taoiseach as a "taking stock" exercise, and it is understood a full British Irish summit has been scheduled for the last week in June. This will be Mr Ahern's first face-to-face meeting with DUP representatives since the party's triumph over the Ulster Unionists in last month's general election.
The Taoiseach will be anxious to establish for himself the extent to which the election campaign has influenced the attitude of the DUP to resumed negotiations about possible power-sharing with Sinn Féin, posited on an IRA initiative apparently thought "imminent".
It is understood the DUP is equally eager to meet Mr Ahern, although for different reasons. According to senior sources the Taoiseach may come under pressure to explain why investigations into alleged IRA money- laundering operations have apparently "gone quiet".
The meeting will also be attended by the Minister for Justice Michael McDowell and the Minister for Foreign Affairs Dermot Ahern.
The suspicion inside the DUP is that this may reflect a political disposition to accept an IRA move - in response to Gerry Adams's call on republicans to commit to exclusively peaceful and democratic means - which DUP politicians expect will fall short of what they call "the Blair necessities" for paramilitary "acts of completion".
Mr Ahern has been anxious to hold the DUP to the terms of last December's failed "comprehensive agreement".
However, in a significant hardening of its position, the DUP entered the election apparently committed to end the d'Hondt formula which would provide for Sinn Féin's automatic entry into a power-sharing executive.
Following his post-election meeting with Mr Blair last month, Dr Paisley also questioned the need to organise any devolved government around the co-equal posts of first and deputy first minister established by the Belfast Agreement.
The other outstanding issue from last autumn's negotiation is policing.
The "deal" offered then by Mr Ahern and Mr Blair ostensibly fell on the demand - supported by London, Dublin and Washington - that the IRA allow a photographic record of weapons decommissioning. In return for that, and the completion of decommissioning, the DUP would have been required by February last to agree the modalities for the future devolution of policing and justice powers to Stormont.
However, while the DUP is "in principle" committed to the devolution of these powers, party sources insist there is no prospect of a policing and justice ministry being shared with Sinn Féin.
Meanwhile, The Irish Times has learned that a behind-the-scenes tussle is continuing at Westminster over the appointment of unionist nominees to a new list of working peers expected next month.
The DUP is believed to be questioning former UUP leader David Trimble's elevation to the House of Lords, while there are also re- ports that resistance to Mr Trimble's expected honour is also coming from within the UUP.
North Down Assembly member Alan McFarland (55) is today due to declare himself a candidate for the leadership of the UUP. The former British army major has decided to enter the race to succeed Mr David Trimble against fellow MLAs Sir Reg Empey and David McNarry.