The warning came as the political parties prepared to return to Stormont Castle today in another attempt to break the deadlock over the Ulster Unionists' refusal to let Sinn Fein join Northern Ireland's new executive body before the IRA has begun to decommission its weapons.
Tony Blair and Bertie Ahern, his Irish counterpart, are on standby to fly to Belfast if there is any chance that their presence would push the parties over the finishing line.
But the prospects look gloomy, and the two leaders will decide in the next two weeks whether to implement their plan to "park" the talks until after the European Parliament elections and the annual marching season this summer.
Meanwhile, a warning was given that the peace process was now " in very deep crisis".
Mitchel McLaughlin, the chairman of Sinn Fein, said: "Our view is if you park the peace process there will be no Good Friday Agreement to come back to. It will be gone. There will be nothing to come back to."
He warned that the Unionists would exploit the marching season and told the two governments: "You can't afford even to consider for a moment parking the peace process."
Speaking on BBC1's On the Record programme, Mr McLaughlin urged the Government to reject Unionist calls for a suspension of the `prisoner early release' scheme because of the continued impasse in the peace process. "In terms of prisoners, if there was any attempt of political interference or to suspend, remove or break the commitments given in that particular section of the agreement that would be a deal breaker for Sinn Fein," he said.
But Sir Reg Empey, a leading Ulster Unionist, insisted there was a "very strong case" for halting the releases "because at the present moment you could very clearly argue that people have not honoured their commitments".
There was enormous disquiet in the Unionist community about the release issue, he said. The Unionists and Sinn Fein reacted coolly to a compromise aimed at ending the deadlock by John Hume, leader of the Social Democratic and Labour Party.
He proposed that to boost confidence, all parties, including Sinn Fein, should make a pledge to non-violent means and agreement to self-expulsion from the province's hovernment if they, or any organisation connected to them, went back to bombing and shooting.
But Gerry Adams, the Sinn Fein President , said: "There is no question of us getting involved in any self-expulsion," he said.
In Dublin yesterday, Mr Ahern urged the parties to move forward and warned them of the danger of public support for the peace process ebbing away.
"We cannot afford to wait too long and let the support that we need on all sides to sustain the agreement on a long term basis seep away," he said.
Mr Ahern was addressing members of his Fianna Fail party at a commemoration of the Easter Rising.Reuse content