Leaders of Bosnia's three major ethnic groups have reached an accord designed to unify the Balkan country by remaking the government's constitution a decade after a bloody civil war.

Announcing the accord, Secretary of State Condoleezza Rice called it historic. She said it was "an example of how diverse people can live together without fear."

While leaving details for later, the pact would have Bosnian leaders consolidate power in what would be a stronger national government.

The accord, coming a day after the 10th anniversary of the Dayton accords that ended the three-year war, marks a major step in binding the wounds left by what was Europe's worst fighting since World War II. The conflict killed 260,000 people and drove 1.8 million from their homes.

"Today, Bosnia-Herzegovina is joining the international community," Rice said at a State Department luncheon Tuesday that blurred partisanship by paying tribute to the Clinton administration for brokering the Dayton accords.

Rice said while the Dayton agreements were right for the time, Bosnia needs a stronger, energetic state "capable of advancing the public good and securing the national interest."

Two separate agreements were signed before the luncheon by Rice and Bosnian Foreign Minister Mladem Ivanic that formalized U.S. military access to Bosnia and to govern civil aviation there.

The leaders of the major communities, Serb, Croat and Mulsin, issued a statement. It said:

"We have decided to embark upon a process of constitutional reform that will enhance the authorities of the state government and streamline parliament and the office of the presidency."

"These are only the first steps," the agreement said. "We recognize that further reforms of the constitution will be necessary" to meet criteria for membership in the European Union.

"We are committed to working together to undertake these reforms and to improve the quality of life for all citizens of Bosnia and Herzegovina," it said.

Ivo Miro Jovic, chairman of Bosnia's current three-president arrangement, thanked the United States for its support. He said the Dayton accords showed "you cannot accomplish things with war."

In a separate statement the Serb republic reaffirmed its obligations to cooperate with an international criminal tribunal for the former Yugoslavia.

And all of the leaders said they were determined to deliver all persons indicted for war crimes to the tribunal.

The most notorious of these are Radovan Karadzic and Gen. Ratko Mladic, who were indicted 10 years ago by a U.N. tribunal. They were accused of masterminding the brutal Bosnian Serb offensives against rival Bosnian Muslims.

Leaders of the Serb republic called on them to surrender voluntarily "and by that act express their responsibility" towards the citizens of the Serb republic and Bosnia, itself.

"There can be no more excuses, no more delays," in bringing them to justice, Rice said.

A decade after a bloody three-year war gave way to an ethnically divided government, the agreement to overhaul the constitutional structure was signed Monday night after three days of negotiations overseen by U.S. diplomats.

The statement signed by representatives of the Croats, Serbs and Muslim political groups commits the parties to work out the details by March 2006, the official said.

The agreement was in line with a framework proposed last month by Undersecretary of State Nicholas Burns during a trip to the region.

The new compact modernizes the decade-old accord. It would replace a three-presidents arrangement with a single president and hopefully point the way to a strong prime minister and a strong parliament.

Burns said Monday the idea was to have political party leaders work out the details before elections next year.

Six months ago, while Burns was in the capital of Sarajevo, a major step to reform was taken when a single defense ministry was formed out of two armies, two defense ministers and two chiefs of staff.

The agreement commits all sides to eliminate redundant offices and to clean up inefficiencies -- necessary steps toward including Bosnia eventually in the European Union, which would enhance the country's economic fortunes.

For Rice, the accord represents a double-fisted diplomatic triumph. Only last week, in Jerusalem, she applied the finishing touches to an agreement between Israel and the Palestinians that opens the borders of Gaza and eases movement by Palestinians.

Bosnia currently has a weak government. For example, there are 14 education departments. European leaders have warned that the situation had to be revised for Bosnia to enter the European Union.

In rare tribute by a Bush administration official to its predecessor, Burns praised the accords reach in Dayton, Ohio, "as a seminal moment in American diplomacy."

Nevertheless, Burns said, "Simply put, the Dayton Accords need to be modernized. They served Bosnia well over the last decade, but they were never meant to be immutable or set in stone."

Without change, "It will mean there's no horizon for the country, that there's no chance for them to join the European Union," he said Monday at the U.S. Institute of Peace, a government-funded think tank. "Bosnia can't remain a fractured state and think it can take its place in Europe."