Balkan leaders returned home Wednesday to sell the Ohio summit peace agreement to their skeptical people as Bosnian Serb hardliners vowed to block the plan.

Bosnian government leaders returned to cheering crowds in Sarajevo and said there was no time to lose in moving to implement the historic agreement."We must start as soon as possible, we cannot lose a single day," Bosnian Prime Minister Haris Silajdzic told Reuters.

But of Serbian nationalist hostility underlined problems ahead for enactment of the three-nation pact ending more than four years of war in former Yugoslavia between Serbs, Croats and Muslims.

Many people hoped the accord would hold but expressed doubts about the ambitious agreement, which calls for a territorial split between a Muslim-Croat federation and a Serb entity.

The peace deal, signed in Dayton, Ohio, by the presidents of Serbia, Croatia and Bosnia after three weeks of intensive U.S.-led mediation, will be supervised by up to 60,000 NATO peacekeepers.

Serbian state media portrayed President Slobodan Milosevic as a hero upon his return to Belgrade.

"A just peace for all the nations living in this region has been achieved," he said at Belgrade airport.

Washington expressed confidence that Milosevic would thwart any attempt by Bosnian Serb politicians to disrupt the peace plan.

"The war is over, and (the Bosnian Serbs) have to realize that the war is over. They can't refight the war," State Department spokesman Nicholas Burns told a news briefing.

While Milosevic looked forward to the planned suspension of U.N. sanctions against rump Yugoslavia, Bosnian Serbs were implacable.

Momcilo Krajisnik, a hard-line member of the Bosnian Serb leadership, boycotted the initialing ceremony and warned: "What has been done is an especially big mistake."

There was silence from Bosnian Serb "president" Radovan Karadzic and army commander Gen. Ratko Mladic, both accused of war crimes by the United Nations and destined to be removed from power under the agreement.

The hard-liners were expected to call a session of the Bosnian Serb parliament, which they control, to try to reject the plan, which legalizes a Bosnian Serb republic on 49 percent of Bosnian soil.

Krajisnik said that although Milosevic took a Bosnian Serb delegation to the summit, they saw the maps with the territorial split only 10 minutes before the agreement was initialed.

Croatian President Franjo Tudjman arrived in Zagreb to a tepid reception from newspapers which claimed he endorsed too many concessions to Milosevic.