Mr Trimble, who is also the Northern Ireland Assembly's first minister, was speaking ahead of a week of renewed negotiations to find a solution to the stalled process.

UK Prime Minister Tony Blair and his Irish counterpart Bertie Ahern are expected to mount another attempt to restart the peace process on Thursday.

Most of the political parties involved will hold separate meetings on Monday to formulate their opinions on the Hillsborough declaration proposed by the two prime ministers.

Northern Ireland Secretary Mo Mowlam will lead discussions between the pro-agreement parties on Tuesday.

She will be joined in this by the Irish Foreign Minister David Andrews and his Junior Minister Liz O'Donnell.

David Trimble: "Are republicans committed to the agreement?"

Mr Trimble said the declaration had the "potential" to work but questioned the republicans' commitment to the peace process.

At the weekend, Sinn Fein chief negotiator Martin McGuinness warned his party - which he said had convinced many "sceptical republicans" to sign up to the Good Friday Agreement - could not deliver support for what amounted to a renegotiation.

But Mr Trimble said: "What is at stake here is a question of whether Mr McGuinness and Mr Adams and the people for whom they speak are actually committed to the agreement or not.

David Trimble: "I think we need to wait and see what their position actually is"

"Mr McGuinness is saying that some of his followers are not.

"But the question is whether the organisations for which they speak are committed to the agreement and are prepared to turn their back [on violence]."

Unionists refuse to form the assembly's executive with Sinn Fein until the IRA begins disarming its weapons.

Martin McGuinness: Peace under threat

Sinn Fein, the political wing of the IRA, insists decommissioning was not a precondition set out in the Good Friday Agreement.

Mr Trimble has told Ulster Unionist assembly members he has drafted a resignation statement to be issued if Mr Blair goes back on promises to exclude Sinn Fein from the executive if there is no IRA decommissioning.

The discovery of two firing packs for ground-to-air missiles in countryside near Pomeroy, Co Tyrone, on Monday, has underlined unionist calls for decommissioning to begin.

Two used battery packs for the SAM 7 missile, believed to be in the possession of the IRA, were discovered by army bomb experts.

UUP security spokesman Michael McGimpsey, said: "This reinforces the absolute requirement for decommissioning and, we believe, vindicates our position on this matter."

Doubts over declaration

The Hillsborough declaration, issued two weeks ago, sets out a timetable for forming the executive and disarming paramilitary weapons.

Several Ulster Unionists, including Lagan Valley MP Jeffery Donaldson and assembly members Derek Hussey and Pauline Armitage, have expressed doubts about the document.

Seamus Mallon: Price of failure is too great

But Mr Trimble said republican statements over the past two weeks had not used the usual IRA language of adamantly refusing to decommission.

However, Northern Ireland Deputy First Minister Seamus Mallon has criticised the IRA's comments that it was "unimpressed" by the Hillsborough declaration.

Mr Mallon rejected the IRA's claims that the declaration was a re-writing of the agreement.

He was pessimistic about the chance of a breakthrough this week.

However, the SDLP MP warned the parties that the dangers of walking away were great.