The IRA has started a process to put its weapons beyond use, the head of the International Commission on Decommissioning announced yesterday.

The move came as the parties in Northern Ireland faced new pressures to sign up to a package of proposals to end the deadlock on decommissioning threatening the Good Friday Agreement.

In yesterday's dramatic development, General John de Chastelain revealed that the Provisionals had proposed a plan to deal with guns ,which involved no risk to the public and prevented dissident republicans seizing them.

General de Chastelain said he was satisfied that the IRA proposal met his commission's remit from the British and Irish governments.

"We believe this proposal initiates a process that will put IRA arms completely and verifiably beyond use," he said.

His assessment raised hopes in London and Dublin that the way was now clear for an early agreement on decommissioning. But with unionists demanding destruction, the absence of details of how this process will be carried out still left the two governments facing a deepening crisis which could mean the suspension of the Stormont Assembly by the end of the week.

Sinn Fein president Gerry Adams said the commission's statement marked a "hugely historical breakthrough".

Northern Ireland Secretary John Reid and the Republic's Premier, Bertie Ahern, said the potential was now there to resolve the one major obstacle threatening the future of the power-sharing administration.

But it failed to end the lingering doubts of Ulster Unionist leader David Trimble's senior party officers who were meeting in Belfast last night. Mr Trimble said: "The IRA has taken a significant step towards decommissioning, but it hasn't actually begun decommissioning."

All parties had been given until last night to respond to the take-it-or-leave-it Anglo-Irish package of proposals prepared by Prime Minister Tony Blair and Mr Ahern aimed at saving the agreement and the assembly.

But with republicans also seeking new concessions on policing and security measures, the process has been delayed.

The Government has until tomorrow, or Thursday at the latest, to decide where to go from here. After Mr Trimble's resignation six weeks ago, a new First Minister must be appointed by midnight on Saturday.

Without actual IRA decommissioning, London will probably be forced to re-introduce direct rule.

The IRA controls a vast arsenal of guns and explosives. Two of its arms dumps have been checked three times by Government-appointed inspectors who confirmed none of the weapons had been touched.

Security sources said last night the IRA was likely to put weapons "beyond use" by sealing the bunkers permanently with concrete.