The Taoiseach and the British prime minister are continuing crucial talks with Northern Ireland parties this evening in an effort to restore devolution.
The talks, being held at Leeds Castle in Kent, centre on the chances of an agreement between the Democratic Unionist Party and Sinn Fein on the issue of the IRA.
A Sinn Fein spokesman revealed its negotiators had held several intense meetings with the two premiers in a bid to achieve movement on their key demands.
The spokesman said: "The Sinn Fein negotiating team is currently locked into discussions with the two governments. Gerry Adams and Martin McGuinness have now met the Taoiseach and the British Prime Minister a number of times."
"The DUP continue to refuse to speak to Sinn Fein and their anti-agreement demands, expressed publicly again today, are unacceptable," he added criticising the DUP.
Ealier today the British Prime Minister Mr Tony Blair tonight delivered an ultimatum to all sides in the Northern Ireland peace talks - this is decision time.
"We can't go out of this and have another set of elongated negotiations,"Mr Blair said.
The DUP leader, Mr Ian Paisley, who travelled to Kent overland after doctors advised him against flying, sounded a hardline message. "Gerry Adams can waffle until the cows come home, I'm not talking to Gerry Adams. I'm talking to the British Prime Minister to get him to keep his promises," he said.
Mr Adams indicated unionist concerns around IRA activity and decommissioning could be resolved, but he was adamant again yesterday that Sinn Féin would not tolerate any alteration to the fundamental architecture of the Belfast Agreement.
Speaking as he arrived in Leeds Castle this morning, Mr Adams said there could be no preconditions in the talks.
"We are here as a fully mandated party. We are here on the same basis as those other parties and we are here also as the largest nationalist party on that part of the island," he said.
"We would be quite pleased to vote for Ian Paisley as First Minister, but in the context of the Good Friday agreement," he added.
However, the DUP deputy leader Mr Robinson, in today's Irish Times, has indicated this could be one of the main obstacles to agreement. "The institutions of the Belfast Agreement failed to provide good government and must be changed," he writes.
"There will have to be complete decommissioning in a way that is transparent, conclusive and definitive," a DUP spokesman insisted.
As he arrived for the talks, the Ulster Unionist Party leader, Mr David Trimble, said the focus should be on "what caused suspension in the first place, what casued the assembly to collapse two years ago, namely the continuing paramilitary activity particularly by the IRA".
He added: "The governments' focus today should be on Republicans, to see whether Republicans are now finally going to do what they should have done . . . namely to completely decommission, and to operate by exclusively peaceful and democratic means, which necessarily means with no private army."
The Taoiseach and Mr Tony Blair arrived after lunch after Northern Secretary Mr Paul Murphy and the Minister for Foreign Affairs, Mr Cowen, took charge of the first round of talks this morning.
Speaking as he arrived, Mr Blair referred to the call he made in Belfast after the assembly was suspended in October 2002 for all the outstanding issues to be settled once and for all.
"Two years ago I made a speech about acts of completion," Mr Blair said.
"This is the moment of decision as to whether those acts of completion are going to happen or not. We need sustainable, enduring institutions in Northern Ireland."
According to the Taoiseach, only a handful of stumbling blocks remain to be overcome.
He said: "We have been through a fair few castles which I am grateful to the Prime Minister for.
"But it's an issue of whether people actually have the will to conclude the Agreement.
"The people are frustrated with all of us and I accept my responsibility for that. They want to see us bring this thing to an end and four or five issues separate that.
"It's time to come to the end of that sequence."
As SDLP leader Mr Mark Durkan arrived, he said it was time for the paramilitaries and political parties to make their minds up. Along with achieving rock-solid devolution, he called for guarantees that "in future people won't have anything more to hear about the IRA or fear from the IRA".
Mr David Ford, leader of the centre-ground Alliance Party, urged against a quick fix that would solve nothing in the long run.
But he refused to even consider what could happen if the talks fail, calling for all sides to do their bit.
Mr Ford said: "If that's the case, we can move forward from today. We shouldn't be discussing Plan B."
Canadian General John de Chastelain, head of the international disarmament body, has returned to Northern Ireland amid speculation of a big move on weapons.
Further troop cuts in Northern Ireland, an amnesty for fugitive Provisionals, more policing reforms and calls for an inquiry into the murder of Belfast solicitor Pat Finucane will also be on the table.