The Rev Ian Paisley's meetings with the Taoiseach and the British Prime Minister were tonight being billed as critical to hopes for reviving power sharing at Stormont.
Sinn Fein source
As Mr Paisley's negotiating team prepared for separate meetings with the two leaders in London tomorrow, Sinn Féin sources said all sides were looking for a sign that the Democratic Unionists would be prepared to share power.
The source said: "The DUP really is the last piece of the jigsaw.
"Tomorrow could be an historic day. If the DUP were to come on board and signal they would be willing to share power, which is the desired outcome, it would be a very significant prize."
Mr Paisley tonight said more progress was being made on a deal to resurrect devolution.
After what he described as a very intense meeting in London with Northern Ireland Secretary Mr Paul Murphy on the future of the Royal Irish Regiment's home battalion, the North Antrim MP warned that if a deal could not be struck soon, it could be lost forever.
"If Northern Ireland is going to get a fair deal, and it has not got a fair deal so far, it'll get a fair deal now," he insisted.
"If we miss the opportunity, we'll never get this back again."
Northern Ireland Secretary Mr Paul Murphy held separate talks with Sinn Féin and the Democratic Unionists in London today.
Both the DUP leader, the Reverend Ian Paisley and Sinn Féin chairman Mr Mitchel McLaughlin emerged from their meetings tonight with Mr Murphy upbeat about the prospects of a deal.
Last year, the DUP overtook Mr David Trimble's Ulster Unionists as Northern Ireland's largest party and told republicans they would only share power with Sinn Féin if the IRA disarmed and ended all paramilitary activity.
British and Irish officials last week put proposals to the DUP and Sinn Féin aimed at delivering lasting power sharing and removing the gun forever from Irish politics.
Other parties like the UUP, SDLP and the Alliance Party have not been given full sight of the plan.
Sinn Féin and the DUP have raised a number of concerns about the proposals but are expected to give their definitive responses within days.
The DUP, in particular, has been pressing for more clarity on how the IRA could instil more unionist confidence in its disarmament process.
It has been proposed that Protestant and Catholic clergy could witness a decommissioning act but the DUP is believed to be keen on a visual aspect, with either photographic or video evidence.
SDLP leader Mr Mark Durkan has been critical of the package, claiming it is stacked too much in favour of the DUP.
Mr Durkan, in particular, has raised concerns at proposals to replace the system of jointly electing a first and deputy first minister at Stormont with a vote for the entire executive.
PA