SARAJEVO, Bosnia-Herzegovina (AP) _ Two bridges emblematized the conditions in Bosnia two weeks after a peace agreement: U.S. soldiers struggled to build one across a rampaging river, while the other became safe to cross for the first time in nearly four years.

Flood waters and mud are tormenting U.S. Army engineers trying to build a pontoon bridge crossing the Sava River that separates Bosnia and Croatia. The bridge is seen as key to moving in equipment and supplies for the 60,000-man NATO-led force that is to implement the peace agreement signed Dec. 14 in Paris.

In Sarajevo, meanwhile, a French commander strode across the Vrbanja Bridge, where hundreds were felled by snipers during the siege of the capital.

This was the bridge that two young lovers _ he a Serb and she a Muslim _ tried to cross in May 1993. Snipers hit them both, and the bodies lay in a grisly embrace for days before the two sides could agree to stop firing long enough to remove the corpses.

Brig. Gen. Louis Zeller, the commander of French troops in Sarajevo, stood Thursday in heavy snow on the bridge and announced that his troops had taken over the ruined buildings on both sides of the Miljacka river.

French anti-sniper soldiers stood at the four corners of the 80-foot bridge, their rifles aimed and ready.

The area around the Vrbanja bridge was one of the 40 zones cleared around Sarajevo by the two warring factions under the first phase of the peace accord.

``Today, the first phase of the Paris Accord was respected ... with the collaboration of the parties,'' Zeller said. ``We now have control of the most significant (military) points'' in Sarajevo.

Four U.S. C-17s brought 51 GIs and 20 vehicles to the Serbian capital Belgrade Thursday to test a route into Bosnia through Serb-held territory. They reached Tuzla, the hub of the U.S. presence in Bosnia, later in the day.

Air Force Tech. Sgt. George Bedsaul said this alternate route was being used because of the weather in Tuzla and adverse conditions at the Sava River crossing.

``The weather is not cooperating at the river crossing or anywhere else,'' he said and added, ``That's the reason that we're moving things and bringing things in in alternate ways.''

In the southern Mostar area, where flood waters forced evacuation of French soldiers on Wednesday, the rain stopped. But the city was left without three bridges washed away by the floods that also killed an Italian policeman working for the European Union administration of the city and destroyed the French Foreign Legion's camp.

Peace implementation in the city, split between Croats and Muslims, was further hindered by failure of the two mayors to agree on the dividing lines.

In Zupanja, across the Sava River in Croatia, the flooding Sava River flooded a U.S. Army tent camp as soldiers slept early Thursday, embarrassing the military and dealing a setback to preparations for moving American troops over a floating bridge into Bosnia.

The river had been rising for the past two days, swollen by recent rains and melting snow. Military officials had planned to move the engineers out of the flood plain but thought the river would stabilize and decided to wait.