Cracks Threaten Fragile Alliance in the Balkans : Bosnia: Border dispute along river illustrates distrust that is chipping away at the foundation of Croat-Muslim partnership. U.S. knows that federation is key to peace.

KULEN VAKUF, Bosnia-Herzegovina — In the complex patchwork of the Balkan war, this riverfront swatch is a peaceful one. Bosnian Serb rebels have been chased away, ending three years of occupation. And hundreds of mostly Muslim residents are lining up to rebuild their ruined homes.

But trouble on a narrow bridge that spans east and west belies the village’s long-awaited tranquillity. An uproar over a barricade of sandbags and barbed wire illustrates how distrust is tearing at the seams of the Croat-Muslim alliance in Bosnia-Herzegovina--and threatens to unravel delicate U.S.-led peace talks in the region.

A Bosnian police officer, working crossword puzzles on a concrete stoop, guards the bridge’s unobstructed eastern entrance. Overhead, a Bosnian flag dangles from a broken electrical wire.

On the river’s west bank, beyond rickety planks that fill a treacherous gap in the bridge, a Croatian army soldier patrols a shoulder-high mound of sandbags and barbed wire. Above him, a Croatian flag flaps in the autumn breeze.

“All of this over here is Croatia, and all of that over there is Bosnia,” the soldier, Mile Smolcic, said. “I’ve heard adjustments are going to be made to the map.”

The mangled Kulen Vakuf bridge, built years ago across the Una River as a local link for villagers, has been transformed by the Croatian army into a self-proclaimed international frontier--even though the internationally recognized border between Bosnia and Croatia is four miles away.

The two sides are not warring across the disputed divide--the Croats and Bosnians are allies against the rebel Serbs--but the Croatian army has orders not to allow Bosnians to pass the fortification into the village’s western side. The order has infuriated returning Muslims, who made up 95% of the prewar population.

“We don’t care who is Muslim and who is Croat--we just want to live again in our town,” said Mahmut Vajzovic, among the first villagers to return home. “We want freedom of movement. We’ve had enough of this war.”

Kulen Vakuf Mayor Ahmo Mehadzic paced furiously on the bridge over the weekend as a 55-year-old woman, a pig and a sheep were permitted to pass west through the Croatian blockade.

The woman, her hands swollen and bleeding, climbed over the sandbags with a stack of red tiles she needed to fix her leaking roof. The farm animals were let through to provide supper.

“Can you believe we have to negotiate every time someone wants to go across?” Mehadzic asked incredulously. “Nobody should be allowed to suddenly move an international border like this.”

The emotional standoff here, though involving only a small village in a small corner of northwest Bosnia, reflects deepening--and potentially calamitous--fissures in the fragile Muslim-Croat alliance, the greatest diplomatic achievement of the 42-month-old Bosnian war.

The bridge dispute strikes at the heart of Bosnian insecurities about their Croatian allies, who have long been suspected of eyeing Bosnian territory. Over the summer, Croatian President Franjo Tudjman reportedly drew a map on the back of a dinner napkin showing Bosnia meted out between Croatia and Serbia, and even today, Croatian government officials do not rule out such a scenario.

“Croatia would rather have Bosnia-Herzegovina remain as a whole state, but if that is not possible . . . Croats there would have no other option than to create some sort of connection with Croatia,” said Bosiljko Misetic, Croatia’s deputy prime minister.

For the past 1 1/2 years, Muslims and Croats in Bosnia have been on the same warring side, thanks to a U.S.-brokered agreement between Tudjman and President Alija Izetbegovic, who heads the Muslim-led but secular Bosnian government. The so-called Bosnian-Croat federation turned a chaotic three-way war--in which Serbs, Croats and Muslims in Bosnia were fighting one another--into a two-sided conflict.

Without the federation, the current U.S.-led peace effort would be impossible; its collapse, analysts say, would send the talks into a free fall and provoke a bloody land rush across Bosnia by all three ethnic groups.

In talks with Tudjman on Sunday, U.S. Assistant Secretary of State Richard Holbrooke again raised the issue of the federation, which U.S. mediators consider a cornerstone of any peace settlement but which skeptics believe Tudjman only pays lip service to.

“For four years Tudjman has wanted to divide Bosnia,” said Stipe Mesic, a Croatian opposition leader who served in the Yugoslav collective presidency before the breakup of the former federation.

“He believes a multiethnic Bosnia can’t survive because Yugoslavia didn’t. The Americans have to send stronger messages that he cannot divide Bosnia. He thinks he can get away with it.”

The Bosnian allies’ federation has always been a marriage of convenience, not mutual respect, making it vulnerable to the ebb and flow of Bosnian and Croatian self-interest.

Its latest and most serious problems have come as Croatia has gained a clear upper hand in the regional balance of power, fueling fears that Tudjman may try to assemble a “Greater Croatia” including Croat-controlled territory in Bosnia.

Since the Croatian army routed the so-called Krajina Serbs from Croatia in August, the Croatians’ brethren, the Bosnian Croat forces, have made large territorial gains in western Bosnia with the backing of the Croatian army.

“There is no reason to hide the fact that before the federation there was a war between Bosnian Muslims and Bosnian Croats,” said Ivan Lovrenovic, an official at the Bosnian Embassy in Zagreb. “The federation carries the burden of the recent past. Those antagonistic reflexes are not gone.”

In Kulen Vakuf, Croatian soldiers and Bosnian police officers said there have been no such reflexes, that the antagonism has come from above.

Smolcic, the Croatian sentry, said his commander threatened him with 10 days in lockup if he let anyone across the bridge. While he spoke, he smiled at the woman with the red tiles--as she passed with her third load of the day.