Trimble said the Irish Republican Army's offer to put its weapons "beyond use" had raised questions that needed to be answered before he could make a recommendation to the party council.
"We are hoping in the days to come that we will obtain more clarity and certainty about how far the IRA statement goes. We hope we will be able to obtain more information from the government on its position on matters which we regard as matters of our concern," Trimble told reporters outside party headquarters.
The British and Irish governments hope to restore power on May 22 to the Northern Ireland government, created under the peace agreement of Good Friday 1998.
The government's powers were suspended in February to prevent a walkout by Trimble over the arms issue.
Some senior Ulster Unionists have said the unprecedented IRA gesture is inadequate, while others have raised new issues about the future of the Protestant-dominated police force, the Royal Ulster Constabulary.
Trimble said calling the meeting does not mean the UUP has committed yet to any set of proposals. He said he would hold more talks with Britain and other parties in the province's tortuous peace process before making a report to the 850-strong UUP ruling council.
Still, the decision to call the convention kept alive hopes of success for the new peace formula that hinges on a shared government and a vow by IRA guerrillas to bury arms that sustained their long anti-British war.
The Irish Republican Army's political ally, Sinn Fein -- which wants to share power with Unionists -- welcomed the decision and warned Britain not to bow to Unionist demands for soft-peddling on plans to reform the RUC police.
"The UUP are obviously trying to exercise a veto over political progress," Sinn Fein chief Gerry Adams told reporters.
Concessions on RUC reform or on any other key issues "could undermine entirely the initiative," he said.
"We are pleased that this meeting has been called. We are concerned that the leadership of the UUP didn't call it on the basis of fully embracing, thus far, the (peace formula)."
The decision came as the peace package appeared to be snarled by UUP wrangling over demands for British concessions on police reforms, on the flying of the British flag and the IRA pledge to put its arms "beyond use."
Trimble, who believes that the IRA offer on arms could break new ground, looks forward to the meetings that will lead to his report on the peace package.
"I have yet to formulate what proposals to put to the council and I don't anticipate being able to do so until well into next week.
"It is our view that the uncertainty should end as soon as possible -- that we should clarify as soon as possible ome of the outstanding questions that are in people's minds about this.
"We think it is better to bring things to a head so that we know where we are going," said Trimble, who would be the leader of any new shared government.
A brief period of home rule was ended by Britain in February when there appeared to be no chance of IRA guerrillas disarming. But last weekend the IRA said it was planning to bury its weapons and open its hidden dumps to international inspection.
President Clinton, a key backer of moves to bring a lasting peace to Northern Ireland after three decades of sectarian strife that left 3,600 people dead, cautioned against celebrating progress too soon.
"We're not done yet," he told reporters on the eve of the crucial UUP decision when asked whether he foresaw a situation that would allow him to make a celebratory trip to the province.
The UUP decision heralds a hectic eight days when Trimble is expected to keep up pressure for retention of the name "royal" and pro-British symbols of the largely Protestant police force.
Catholic parties say Britain must not retreat on reforming the police force, which many in the nationalist minority regards as biased against them.