BELFAST (Reuters) - Northern Ireland's U.S. mediator George Mitchell declared Thursday that peace was at last hand in the British province after centuries of violence and mistrust between Catholics and Protestants.

The former senator, whose 11 weeks of painstaking talks have produced a formula that could end years of acrimony between Irish republicans and pro-British unionists, urged skeptics in the Protestant unionist community to back it.

The twin prizes of guerrilla disarmament and stable government, the pillars of last year's landmark Good Friday peace accord, were within reach, he said.

``I believe that there will be full implementation of the Good Friday Agreement including ... all the institutions and the many other measures that are called for in the Good Friday Agreement and decommissioning (disarmament),'' he said in an interview with Reuters and Sky Television.

Mitchell spoke after publishing an anxiously awaited report on his negotiations with parties who have been at each other's throats for 20 months over the timing of Irish Republican Army disarmament and the launch of a cross-party government.

The moribund talks suddenly burst to life this week with reciprocal moves by the key players, including a pledge by the IRA to appoint a go-between to discuss disarmament -- the key unionist demand.

Trimble Facing Unionist Anger

But Ulster Unionist Party leader David Trimble is already facing anger within his party from critics who say they will not be taken in by a formula that lacks an iron-clad IRA guarantee on early disarmament.

Mitchell tried to allay unionist doubters, saying a thriving peace process was the only way to achieve an arms handover, and he assured republicans it was the best way to achieve the new political institutions they wanted.

``It is absolutely certain that if this process fails, if Mr. Trimble is rejected, there'll be no decommissioning,'' he said.

``If one is really concerned about getting decommissioning, as opposed to just talking about decommissioning, then this is the best course forward,'' he said in the interview.

``And it is the best course forward for those who favor... the establishment of all of the institutions called for in the Good Friday Agreement. Because you are not going to have one part of that without the other.''

Mitchell, a consummate negotiator trusted by both sides, was brought in by the Irish and British governments when it appeared the peace pact he crafted in 1998 was in danger of unraveling.

He stressed that talks on disarming guerrillas and creating a coalition government of Protestants and Catholics must take place on the same day and as soon as possible.

There has been widespread speculation the two issues could be in place by the first week of December.

Mitchell Pays Tribute

Mitchell paid tribute to all the players in the negotiations and said there were no outright winners or losers.

``As a result of all these efforts, neither side will get all it wanted and both will endure severe political pain. But there is no other way forward. Prolonging the stalemate will leave this society uncertain and vulnerable,'' he told reporters.

Political leaders lined up to pay tribute to Mitchell's patience and persistence. And they sought to build bridges in strikingly conciliatory statements.

``There is no other way forward and the people will be the real winners,'' Ulster Unionist negotiator Reg Empey said.

Sinn Fein leader Gerry Adams, whose party once said the struggle for Irish unity should be fought with a ballot box in one hand and an Armalite rifle in the other, said: ``Politics works and politics can bring about changes.''

British Prime Minister Tony Blair praised Mitchell for his ``patience, fortitude and skill.'