Under the new proposals, if some paramilitary weapons are handed over during that period, then the executive-in-waiting would resume full powers.
Sources said the two premiers hoped to put the plan to the First Minister, David Trimble, and Sinn Fein's president, Gerry Adams, when they meet in London this Thursday.
The stalemate is due to Ulster Unionists refusing to sit in a power- sharing executive with Sinn Fein unless the IRA starts to decommission. Republicans say that this will not happen.
The new plan involves a transitional executive, which would allow the four main parties - Ulster Unionist Party, the Social Democratic and Labour Party, Sinn Fein and the Democratic Unionist Party - to nominate ministers and choose departments. The UUP and SDLP are each entitled to three places on the 10-strong executive, with Sinn Fein and the DUP taking two seats each.
The opposition spokespeople and associated Northern Ireland Assembly committees would then work alongside civil servants to prepare future work programmes in readiness for devolution some time in October.
A crucial element of the proposal would be that Mr Blair and Mr Ahern would guarantee that full powers would not be transferred from London to Belfast until some weapons were handed over. There would also be pressure on the Sinn Fein leadership to use the intervening period to persuade the IRA to issue a definitive statement that they would not return to violence.
It is difficult to estimate the proposal's chances of achieving a breakthrough, as it has elements of other ideas which have so far failed.
Sinn Fein rejected the declaration by the two premiers, which called for a "day of reconciliation" which involved "putting some arms voluntarily beyond use".
Mr Trimble gave a cool reception to the idea from the SDLP leader, John Hume, that Sinn Fein should agree to expel itself from government if the IRA ever resumed violence. The UUP maintains that it wants "actual" decommissioning before it will share power with Sinn Fein. Senior Sinn Fein figures insist that they cannot deliver this.
This summer will bring heightened tension with fears of increased dissident attacks and ongoing disputes over the annual Orange marches, including Drumcree.
The DUP leader, Ian Paisley, who opposes the Good Friday Agreement, has vowed to turn the 10 June European election into a second referendum on the peace accord.
Confidence in the peace process could ebb if a definite solution to the decommissioning impasse is not found soon.Reuse content