BOSNIAN SERB FORCES THREATEN U.S. TROOPS : STANDOFF OCCURS AT WAR CRIMES SUSPECT'S CAMP.

Byline: Ron Kampeas Associated Press 

Bosnian Serb threats to fire on American helicopters triggered a weekend standoff between Bosnian Serb forces and U.S. troops, a U.S. commander said Sunday.

The threats prompted U.S. soldiers to make a show of force and their commanders to make a series of late-night phone calls to Serbian President Slobodan Milosevic. It was one of the tensest situations yet for U.S. troops in Bosnia.

The encounter, at the compound of Gen. Ratko Mladic, highlighted the volatility of any effort by peacekeepers to confront the two highest-profile war crimes suspects in Bosnia's 3-1/2-year war: Mladic and Bosnian Serb leader Radovan Karadzic.

Lt. Gen. William Carter, chief of staff of the NATO-led peace force in Bosnia, outlined the chain of events that ended Saturday evening when Bosnian Serb forces backed down and allowed a U.S. inspection of a compound at Han Pijesak, a Serb-held mountain village in eastern Bosnia.

Tensions began Friday, when U.S. helicopters belonging to the 2nd Brigade of Task Force Eagle overflew Han Pijesak to verify a sighting of five Bosnian Serb armored vehicles. The vehicles were reportedly outside areas designated for their storage under the Dayton peace agreement.

Carter said reports identified the five vehicles as a T-34/85 and two T-54/55s - Soviet-designed tanks capable of firing armor-piercing ammunition - and two BVP M-80s, Soviet-designed infantry fighting vehicles with anti-aircraft capabilities.

The war machines had moved about 300 yards from the storage area and entered Bosnian Serb military headquarters.

``Some junior (Bosnian Serb) officers overreacted and made some statements to the 2nd Brigade of Task Force Eagle that we interpreted as threats, and of course, we don't tolerate that at all,'' Carter told reporters.

Pressed to describe the nature of the threat, he said: ``They have weapons in their possession that can be lethal to helicopters and specifically, the threat was aimed at our helicopters which were operating over the main headquarters.''

In response, the U.S. force moved in about 20 fixed- and rotary-wing aircraft and more than 20 armored personnel carriers, and began setting up a communications post.

``It was a very aggressive response on our part, I'll grant that, but we don't intend to tolerate any threats against us,'' Carter said.

The situation had not calmed by Friday evening, and NATO commander Adm. Leighton Smith phoned Milosevic, the Serbian president, to urge him to press the Bosnian Serb military to back down, Carter said.

When a British officer entered Mladic's compound to negotiate Saturday, about 200 Bosnian Serbs mobbed his escort of U.S. troops, cursing, waving Serb flags and pounding on the Humvees. Other Bosnian Serb civilians blocked roads into the village.