The president of Sinn Féin, Mr Gerry Adams, and a party delegation are meeting British government officials again today as efforts to reach agreement on a restoration of devolution continue.
Sinn Fein chairman Mitchel McLaughlin
Before the meeting party chairman Mr Mitchel McLaughlin said they were getting increasingly concerned at the "continuous shifting back of deadlines".
The meeting comes as the Government indicated it did not believe a deal would be struck this week.
Up to now, the Taoiseach, Mr Ahern, and other senior Government figures held out hope that an agreement could be formally agreed in Hillsborough on Friday.
The issue of photographic verification of IRA decommissioning, which the DUP demands, could yet scupper hopes of a deal being signed next week.
Officials believe high-risk, high-stakes brinkmanship game being played by the DUP and Sinn Féin could hamper the prospects of a deal being formalised next week.
Both parties clashed last night over the Rev Ian Paisley's comments that the IRA must apologise for past violence, donning a sackcloth and ashes.
After a meeting with Mr Ahern in Dublin yesterday, the Mr Adams expressed concern efforts to achieve a deal were being dragged out. Mr Ahern told the Dáil last night it was looking like a deal would not be struck by Friday.
Speaking to journalists just before the Sinn Fein delegation went into No 10 Downing Street, party chairman Mr Mitchel McLaughlin said: "We have come to a fairly advanced stage in this phase."
"There are a number of issues that we are still discussing with the British government.
"On Monday, for example, we focused very strongly on demilitarisation. We have made a very, very strong case indeed for a programme that kicks in almost immediately because it is our view that, at this stage in the peace process, we need to see the blight of British military installations removed.
"Our approach throughout this entire process has been to bring the DUP on to the ground of power-sharing and working with all the mandated parties in the North to properly give political leadership and devolved government to the people of the north.
"And to achieve that by ensuring that that is done entirely on the blueprint and the template of Good Friday Agreement. That remains our aim today."
He added: "We are getting very, very concerned indeed about the continuous shifting back of deadlines. It is time to bring this phase of the process to a conclusion."