RAMALLAH, West Bank - Mahmoud Abbas was elected Palestinian Authority president by a landslide, results showed today, giving the pragmatist a mandate to resume peace talks with Israel - but also leaving him with the tough task of reining in powerful armed groups.

Israeli leaders welcomed Abbas' victory, but said they will watch closely how hard he tries to subdue militants. Abbas could easily lose his political capital over a major bombing or shooting attack, and while most militant groups signaled they are willing to give him a chance, not all have signed on to a truce with Israel.

Still, Abbas' victory held out the promise of a new era after four decades of chaotic and corruption-riddled rule by Yasser Arafat, who died Nov. 11. Abbas, who has spoken out against violence and has the support of the international community, promises to reform the government and the unwieldy security services.

Many Palestinians had high expectations of Abbas, widely known as Abu Mazen. "Today is the beginning of a new future," said Sami Radwan, 55, a restaurant owner in Gaza City. "Abu Mazen is the right choice. He is the one who can bring us peace, good business and security."

Final results today gave Abbas 62.3 percent of the vote. His main challenger, independent candidate Mustafa Barghouti, won about 20 percent, an election official said. The remaining five candidates scored in low single digits.

In his acceptance speech, Abbas said he faces a difficult mission, but he reiterated that he would not go after militants. Instead, he said, he wants to "give our fugitives a life of dignity," referring to those wanted by Israel.

"I present this victory to the soul of Yasser Arafat and present it to our people and to our martyrs," Abbas added.

After exit polls predicted a sweeping Abbas victory, cheering supporters took to the streets of the West Bank and Gaza late Sunday. Gunmen fired in the air, motorists honked horns and members of Abbas' ruling Fatah movement, wearing checkered black-and-white headbands, danced in the streets.

The Islamic militant group Hamas, the largest opposition group, announced today it will work with Abbas, despite misgivings about what it said were voting irregularities, including a decision to keep polls open two hours longer than planned. Hamas had called for a boycott of the election, but did not try to disrupt the vote.

A U.S. observer team headed by Sens. Joseph Biden Jr., a Democrat from Delaware, and John Sununu, a Republican from New Hampshire, said in a statement that the Palestinians "have conducted a clean, open and fair election, largely unimpeded and without interference."

In Washington, President Bush called the election a "historic" step toward a Palestinian state.

"The United States stands ready to help the Palestinian people realize their aspirations," Bush said. "The new Palestinian president and his Cabinet face critical tasks ahead, including fighting terrorism, combatting corruption, building reformed and democratic institutions and reviving the Palestinian economy."

It wasn't clear how many people voted.

Officials said close to 70 percent of 1.1 million registered voters cast ballots. But because elections officials opened up the polls to all Palestinians above age 18 in the middle of the day on Sunday, about 660,000 others could have voted; officials hadn't yet said how many did.

David Pearce, the U.S. consul in Jerusalem, said he was struck by the civic pride of the voters and their new sense of hope. "There are immense challenges. A million things can go wrong. But for the first time in a long time, there is a chance that something can go right," Pearce said.

In Israel, a new, more dovish coalition was to be approved by parliament today, another step toward a planned withdrawal from the Gaza Strip and four small West Bank settlements in the summer.

Prime Minister Ariel Sharon's new coalition partners, the moderate Labor Party and a small ultra-Orthodox faction, ensure a parliamentary majority for the pullback, despite fervent opposition from hardliners.

Sharon plans to meet with Abbas soon, the Israeli leader's aides said.