David Trimble, the Ulster Unionist leader, has attacked Tony Blair, the prime minister, for buying time in dealing with the Irish Republican Army (IRA), while joining international efforts to fight terrorism, in a newspaper article.

Writing in the Daily Telegraph on Monday, Mr Trimble praised Mr Blair's support to president George W. Bush in fighting terrorism following the attacks on the US in September 11, but blamed Mr Blair for the "government's stance on domestic paramilitarism."

"If Tony Blair had firmly insisted on the basic principles of the agreement,...whereby the Provisionals' (IRA's) participation in full democratic politics would be linked to their adherence to constitutional norms -- then the finest achievement of his first term would not be in such a desperate condition," he wrote.

On Sunday John Reid, Northern Ireland secretary, stepped up pressure on the IRA to disarm, claiming the fragile peace process depends on a move on weapons.

His warning came as sectarian violence broke out again on Sunday night in north Belfast. Stones, bottles and fireworks were thrown as loyalist paramilitaries were accused of trying to goad republicans into retaliation.

Dr Reid urged republicans to honour their pledges on decommissioning, saying: "If they do, I believe we can get a new dynamic; if they don't, then I think we have a very serious problem."

The province's political parties have six weeks to save the Good Friday agreement and resolve the issues of disarmament, demilitarisation and policing after Dr Reid suspended the devolved institutions for 24 hours from midnight on Saturday. It was the third time that the power-sharing assembly and executive had been suspended.

Meanwhile, Mr Trimble has prepared a bid to oust Sinn Fein ministers from the Stormont power-sharing executive.

The former first minister will table an assembly motion on Monday calling for Martin McGuinness, education minister, and Bairbre de Brun, health minister, to be excluded because of the IRA's failure to put its weapons beyond use.

Although the motion seems certain to fail the required cross-community test, Mr Trimble then plans to pull his ministers out of the executive. Unveiling his tactics, Mr Trimble said: "That will bring matters to a head."

In these circumstances, Mr Trimble explained, the three UUP members of the Executive, Sir Reg Empey, Michael McGimpsey and Sam Foster, could not continue in their posts.

"It would be impossible to do so," he told BBC Radio Ulster. "We could not do so credibly; we will not do so."

Mr Trimble's effort to up the stakes came amid re-ports that the IRA was set to seal two of its arms bunkers before the end of the year. However, Dr Reid insisted that he had no knowledge of such moves and called the reports "mischievous".

Mr Trimble was backed by a senior member of the nationalist SDLP, who insisted it was down to the IRA to rescue the three-year-old Belfast accord. Brid Rodgers, agriculture minister, urged the republican movement not to fall into the trap she claimed was being laid by hardline unionists.

She said: "My message to the IRA is blunt and to the point: a section of unionism is hell-bent on wrecking the agreement and defy the express will of the Irish people.

"You are playing into their hands. Only the IRA have it within their power to save the people's agreement."

However, Gerry Kelly, a senior Sinn Fein negotiator, accused Dr Reid of ignoring the Belfast accord by his actions.

The North Belfast assemblyman said: "Suspension is not under the Good Friday agreement."

"It's the British government and John Reid trying to focus all attention on arms when they need to look at why these institutions are being brought down."

Mr Kelly also poured scorn on any suggestions of an impending move by the IRA on decommissioning, saying: "There's no sense that they are shifting their position."