The peace process in the North had reached its "most significant defining period" so far and the IRA was facing a "big decision" that would challenge everyone else in the process to respond appropriately, according to Sinn Féin chief negotiator Martin McGuinness.
Mr McGuinness told The Irish Times he expected a major effort by Downing Street to revive the process after this week's general election.
"I am quite convinced that if Tony Blair is returned, and it is looking likely, he will mount a huge effort to try and break the deadlock and to get the peace process and the Good Friday agreement back on the road again."
Asked if the IRA would still exist in a year's time, he said: "IRA volunteers want, as passionately as I do, to see the peace process succeed. Obviously we are at a critical phase and, in my view, the most significant defining period that this process has ever seen."
He said Sinn Féin leader Gerry Adams had "appealed to IRA volunteers to accept his analysis that the best way forward now for republicans is by purely political and democratic means and that they should be involved in no activity whatsoever.
"No activity means no activity," Mr McGuinness said. "It means no activity whatsoever which would undermine the peace process. Now the IRA has big decisions, or a big decision, to make as a result of that."
Describing Mr Adams as "the effective leader of Irish republicanism", Mr McGuinness said: "His words have to weigh very heavily with IRA volunteers all over the island."
The IRA decision to call and sustain its 1994 ceasefire had been "an incredible contribution" to building the process.
He added: "It is certainly my passionate hope that, whenever their deliberations are concluded, the IRA will accept what Gerry Adams is saying and so, in many ways acting in a unilateral fashion, do what they did in 1994, effectively put it up to everyone within the process to make their contributions also."
Asked if this meant the disbandment or standing-down of the IRA, he said: "No, I think it's about an adherence to his belief that the best way forward is by purely political and democratic means.
"What shape or form that takes is a matter clearly for them but if you are in a situation where the IRA is not involved in anything, and I mean anything, then obviously that propels the whole situation into an entirely different ball-game."
Asked if the IRA, which was revived during the attacks on Catholic communities in Belfast in 1969, would still see itself having a role as a reserve force for the defence of nationalist areas, Mr McGuinness said: "Given what we have been through over the course of the last 30-odd years and the hugely high level of politicisation which exists within republican areas, I don't think anybody ever envisages again a time when nationalist communities will not be in a position to defend themselves in a crisis. The big difficulty with that is that I am working to ensure there are no crises within the process."
Commenting on forecasts of further decline in the position of the Ulster Unionist Party in this week's election, Mr McGuinness said: "It is one of the great annoyances that I have in the process. I believe David Trimble has been the author of his own misfortune."
The UUP leader would be in a much stronger position today if Mr Trimble had put "his arms around the Good Friday agreement" and stayed in the power-sharing institutions, instead of bringing them down.
"I mean that very sincerely. It is one of the great irritations and annoyances that I have experienced in the course of recent years to see the state into which the Ulster Unionist Party has fallen as a result of their failure to fight for the Good Friday agreement and to embrace change," Mr McGuinness said.
SDLP leader Mark Durkan said yesterday the appeal to the IRA from Mr Adams showed how Sinn Féin was only catching up now with the position of his party and others, who had said the IRA was an obstacle to political progress for years.
Former SDLP leader John Hume also criticised Mr Adams: "I have no doubt that in this election the people, in very large numbers, will stand shoulder-to-shoulder with the SDLP, in total support for the consistent work of the party."
Meanwhile, Mr Adams held a May Day press conference in Belfast outside the former Falls Road home of executed 1916 leader James Connolly. Asked about reports of an IRA leadership "reshuffle" he said: "I don't know anything about it."