In an unprecedented move Tony Blair made it clear he wants to enlist John Major, the former prime minister, and William Hague, the leader of the opposition, in the campaign to win a "Yes" vote in 22 May's crucial poll. US president Bill Clinton will also visit the province in the week before the referendum, effectively endorsing the deal.
The initiative came as Mr Trimble overcame bitter internal criticism when he opened his campaign to market the far-reaching initiative to the Protestants of Northern Ireland.
Amid the jeers of Paisleyite protesters, his party's executive committee voted 55-23 in support of the agreement, recommending it to the much larger meeting of the party council next Saturday. Mr Trimble declared: "There are many serious reservations about the agreement. But we have to make a decision."
However, the prospect of a serious split within the Ulster Unionists could cast a shadow over the Yes campaign. After leaving yesterday's tense meeting, West Tyrone MP William Thompson said bluntly: "I will never accept this agreement. It is a disaster. I think the party is extremely divided on this issue."
His colleague William Ross, MP for Londonderry East, warned that Mr Trimble had not yet won the battle. "I am very disappointed but the next step is the full council meeting next week," he said.
There was criticism, too, from Lord Tebbit, whose wife Margaret was paralysed in the IRA's Brighton bomb. He described the deal as "a considerable victory for the IRA". Critics are unhappy about the imminent release of many convicted terrorists.
But Mr Blair made it clear he would extend his political support to those in favour of the agreement, going out of his way to praise Mr Trimble. A Downing Street source said the UUP leader had "guts and intelligence" and that the people of Northern Ireland had to decide "whether to go with the people who don't want peace or with the people who have the guts to sit down and get an agreement in place".
Mr Blair hopes to enlist the backing of Mr Hague and Mr Major. A Conservative Party source said no decisions had yet been taken, but pointed out that both men had welcomed the deal warmly and are likely to be supportive of the Yes campaign.
Mr Blair, now on his Easter break at the island retreat of the Spanish prime minister, Jose Maria Aznar, said: "I think it's time for the men of vision, not for the people of history, to say: whatever the past, we are going to drive this thing through."
Describing the last days of the talks, he admitted there were "quite a few moments" when he thought success was not possible. "It was about 4 o'clock on Friday morning when I thought we were going to lose it, just because of overcoming so much history from the past.
"I was just absolutely determined as I think everybody else was. I had almost made up my mind that I wasn't going to leave until we had an agreement."
Mr Trimble and his supporters will feel they have made a good start in selling such a radical new departure to a party notoriously suspicious of innovation. They and the opposing faction will work hard next week to muster support for their positions at the meeting of the party council.
A quieter process of assessment was meanwhile taking place within the Republic, where Sinn Fein and the general nationalist community are absorbing the document. No major eruptions of opposition were visible yesterday.Reuse content