U.N. Observers Due in Sarajevo Today : Balkans: Peacekeeping plan will be tested. The Pentagon warns against commitment of U.S. troops.

Playing down speculation about the need for combat troops, the Bush Administration and the United Nations waited anxiously Tuesday for a cease-fire in besieged Sarajevo so that peacekeepers could start to take over the airport for badly needed relief flights to the starving in Bosnia-Herzegovina.

In New York, the United Nations announced that Canadian Brig. Gen. Lewis Mackenzie will lead an advance party of 30 military observers into Sarajevo today to test whether Serbian militia would allow a battalion of 1,000 peacekeepers to occupy the airport.

The Security Council has authorized the dispatch of the battalion, but only after U.N. Secretary General Boutros Boutros-Ghali can assure it that a cease-fire is firmly in place. The warring parties around Sarajevo reached a cease-fire accord with the United Nations last Friday, but it collapsed in a devastating bombardment of the Bosnian capital over the weekend.

“The indications we have this morning are that it has calmed down somewhat,” said U.N. spokesman Francois Guiliani, “but not enough to allow the opening of the airport.”

In Washington, Pentagon officials privately warned against any commitment of U.S. troops to the conflict and voiced strong objections to use of American forces as peacekeepers at Sarajevo airport, where they would be vulnerable to gunfire from the surrounding hills.

One senior military officer likened the airport’s position to that of Dien Bien Phu, where Vietnamese defeated the French in 1954. Their artillery fire from the hills surrounding the valley where French soldiers were entrenched proved decisive there.

“It would take an enormous number of troops” to hold the airport, the officer said.

Another senior Pentagon official called the possibility of such a deployment “Beirut 2,” referring to the 1983 deployment of Marines at the Beirut airport, where they received regular shellfire from artillery hidden in nearby mountains and ultimately a terrorist attack that killed 241 U.S. servicemen.

“We are not looking for ways to get into that quagmire,” the official said of Yugoslavia. U.S. troops there would have to run a gantlet of antiaircraft fire to get in, would face punishing artillery while there and would have to navigate a deadly terrain of urban warfare waged by regular army units and irregulars, the official said.

“There’s no reason to believe that either side wants it to end,” he said. “It’s not a situation that lends itself to a military solution.”

State Department spokeswoman Margaret Tutwiler defended the Bush Administration from skeptical questions about its willingness to sit back and wait for an elusive truce while people starve.

In reply to a reporter who insisted that the Administration is giving Serbs “a veto over humanitarian assistance to the people of Bosnia,” a clearly annoyed Tutwiler said: “I don’t know of a nation in the world, I don’t know of an international organization, I don’t know of a humanitarian group that is suggesting sending their young people into the current situation that exists in downtown Sarajevo. And that is something . . . we have a totally clean conscience over.”

Tutwiler said she would not answer questions about whether the United States is considering providing military protection for the relief operations.

U.N. Undersecretary General Marrack Goulding also tried to dampen speculation about the use of troops to force the relief supplies through the Serbian lines to besieged Bosnians, most of them ethnic Muslims and Croatians. He told members of the Senate Government Operations Committee that “enforcement is not being discussed at present.”

After meeting with Deputy Secretary of State Lawrence S. Eagleburger, Yugoslav Ambassador Dzevad Mujenzinovic said his Serb-led government in Belgrade supports U.N. attempts to take over the Sarajevo airport. But he repeated his government’s contention that it has no control over the Serbian militia shelling Sarajevo.

This contention is not accepted by the U.N. Security Council.