Hundreds of people in besieged Sarajevo flocked to use newly reopened roads Tuesday, grabbing the chance to make the journey without the risk of being shot.

Witnesses described the scene as orderly chaos as a line of cars stretched back more than one mile to await checks by U.N. peace-keepers.Although the agreement by the Muslim-led government and Bosnian Serbs to reopen the roads eased the grip on the city, an exasperated United States said it was cutting off talks with the Serbs because of what it called their intransigence over an international plan to end the 34-month-old war.

The roads across the airport were opened to civilian traffic Monday for the first time in seven months in line with a cease-fire agreement that started on Jan. 1.

Bosnian Serb besiegers allowed aid agencies to cross last week.

About 300 cars lined up to get out of the Dobrinja suburb on Tuesday morning and others waited to come the other way.

Bosnian police checked lists to ensure prior approval had been gained. U.N. peacekeepers searched the cars, using mirrors to check underneath.

Then, a few at a time, cars were escorted across the frontlines by French U.N. armored personnel carriers.

U.N. peacekeepers said more than 1,000 people from Sarajevo's three communities used the roads Monday to visit neighboring suburbs that have been within sight but kept out of reach by the war.

Serbs traveled between their strongholds of Ilidza and Lukavica. Muslims and Croats drove across the U.N.-controlled airport to and from government-held Butmir and Dobrinja by bus and car. The suburbs ring the airport.

It was another step toward normality after more than 1,000 days of siege. The truce has halted fighting across most of Bosnia except for the northwest Bihac enclave, where Muslim rebels backed by Serbs from neighboring Croatia are battling the government army.

In Washington, a senior official said the United States was breaking off contacts with the Bosnian Serbs because of their refusal to accept a peace plan worked out by the "Contact Group" of the United States, Russia, Britain, France and Germany.

"There's no point in shuttling up the hill from Sarajevo to Pale to listen to the kind of crap which was dished out by (Serb leader Radovan) Karadzic," Assistant Secretary of State Richard Holbrooke said.

The talks with the Bosnian Serbs were initiated last month after mediation by former president Jimmy Carter.