Air Force One took off with Mr. Clinton, first lady Hillary Rodham Clinton, and the official U.S. delegation on board.
During his trip, President Clinton met President Boris Yeltsin in Russia, toured parts of Northern Ireland with British Prime Minister Tony Blair, and met Irish Prime Minister Bertie Ahern in Dublin.
Before departing, Mr. Clinton played a round of golf at the fabled Ballybunion Golf Course.
Also on Saturday, President Clinton appealed to the Irish people never to allow "the enemies of peace to break your will" as Northern Ireland's Protestant leader announced he would finally end his long war of nerves with Sinn Fein.
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"You have made it possible for me...to tell every warring, feuding, hating group of people, trapped in the prison of their past conflict, to look at Ireland and know there can be a better day," Mr. Clinton declared to cheers and applause.
In Belfast, Ulster Unionist Party leader David Trimble scheduled a meeting with Gerry Adams, ending his three-year refusal to talk directly with the leader of the IRA-allied party and providing the White House with its hoped-for outcome from the trip.
Mr. Clinton had urged direct discussions on Thursday when he was in Belfast.
"It's another positive development," said White House spokesman Joe Lockhart.
The meeting between Adams and Trimble will happen Tuesday or Wednesday, said Dermot Nesbitt, a Trimble colleague.
Trimble, the would-be leader of Belfast's unformed new government, and Adams both led their parties to accept April's accord on how Northern Ireland should be governed. Trimble had sat in the same room but refused to talk directly to Adams because of the Irish Republican Army's unwillingness to start disarming as evidence that the outlawed group's July 1997 truce is permanent.
Saturday's decision followed Trimble's announcement earlier that he would lead round-table discussions with all party leaders, including Adams, on Monday in Belfast to start the process of forming a government between the north's British Protestants and Irish Catholics. Sinn Fein wants two of the expected 12 seats in the new Belfast administration.
At Limerick, Mr. Clinton basked in the promise of peace and vowed to ontinue U.S. support.
"Three years ago in Dublin, I promised the people of Ireland that as long as Ireland walks the road of peace, America will walk with you," the president said. "You have more than kept your part of the deal and we will keep ours."
Ahern led the president, Mrs. Clinton, and the crowd in a moment's silence for the latest fatality from political violence in Northern Ireland.
Retired Catholic baker Sean McGrath, 61, died Saturday of his wounds three weeks after an IRA dissidents' car bomb killed 28 and wounded more than 330 people in Omagh.
President Clinton, in his remarks, mourned the Aug. 15 atrocity (the deadliest in Northern Ireland's 30-year conflict), as well as July's burning deaths of three Catholic boys.
"There will be still efforts by the enemies of peace to break your will, to get you to turn back, to get you to lose faith. Don't do it. Don't do it," Mr. Clinton urged the crowd, which braved monsoon-like cloudbursts to see him.
"Remember what it was like when you were here on this day," he said, gesturing past bullet-proof glass walls to the sea of faces, now warmed by sunny skies, filling narrow streets in three directions. "This is you at your best. Do not let them break your will."
Mr. Clinton's visit coincided with a fresh U.S. contribution to Ireland's "Celtic tiger" economy.
Dell Computer Corp., America's largest direct seller of personal computers, announced plans to open a new $90 million factory in Limerick next year.
The company, headquartered in Round Rock, Texas, which located its main European manufacturing site in the city in 1991, already has two plants here employing 2,600 workers, and could add jobs for 1,700 more in the new factory.
Dell also announced it is donating 100 computers to civil authorities in Omagh to help organize reconstruction of the bomb site and coordinate services for victims.
City leaders gave President Clinton Limerick's "freedom of the city", an honorary citizenship also bestowed on President Kennedy there in 1963. Both presidents have Irish ancestry.
"You have made us feel very much at home," a smiling President Clinton said.
The president also received a joint peace prize from the chancellors of all nine universities in Ireland for his support for the 22-month-long Belfast negotiations.