The Ulster Unionist leader has called on the British government to suspend the North's institutions on a short-term basis to provide more time for republicans to begin decommissioning.
Mr David Trimble said there was enough time for such a move by the IRA but in its absence a six-week suspension of the Assembly was his preferred option.
"Even at this late stage the republicans can still save the process and save the Assembly by acting. But if they don't act, then it is they who have put the institutions at risk."
The UUP leader said the IRA's statement was welcome insofar as it confirmed a method for decommissioning had been agreed with the Independent International Commission on Disarmament but the situation could no longer be salvaged by words alone.
A short-term suspension would be "pointless" unless republicans were planning to move on disarmament, he said. "The Secretary of State could reset the clock with a short suspension, but it would lack credibility unless it was clear something was going to happen.
"If he resets the clock for another six weeks with no expectation of anything happening, that would be seen as a transparent gesture."
The suspension of the Assembly in February 2000 had moved the process forward, Mr Trimble said. "It may be that it will work again - that is obviously an option that the Secretary of State has to consider."
He also accused the two governments of having created a "moral vacuum" by basing the peace process on a climate of "empty promises". Their failure to persuade the IRA to disarm was a "great dark stain" on Mr Blair and Mr Ahern's record, he said.
Mr Trimble's party colleagues from both pro- and anti-agreement camps said nothing short of physical disarmament by the IRA would satisfy them. A delegation led by the acting First Minister, Sir Reg Empey, met the Northern Secretary, Dr John Reid, yesterday. Sir Reg said his party would respond positively to further moves by republicans.
"We understand that it's a big problem for republicans dealing with the arms issue. We are not interested in surrender, we are interested in ensuring that everybody who exercises political power in Northern Ireland is committed to exclusively peaceful means."
Sir Reg denied claims by the Sinn Fein president, Mr Gerry Adams, that Ulster Unionist ministers were threatening to resign if Dr Reid did not suspend the institutions.
The party's South Belfast MP, the Rev Martin Smyth, rejected the statement as "cynical choreography" and called on unionists to "hold their nerve and not budge until we see the verifiable and credible decommissioning of arms".
The DUP's deputy leader, Mr Peter Robinson, said it treated the people of Northern Ireland to "prose and posturing" without producing any product.