The international war crimes tribunal is poised to send teams of criminal investigators and forensic specialists into Kosovo with NATO peacekeeping forces and is negotiating with allied military commanders for immediate access to sites of suspected atrocities committed by Yugoslav forces against ethnic Albanians.

The tribunal's chief prosecutor, Louise Arbour, and her deputy, Graham Blewitt, have been laying the groundwork for tribunal personnel and other experts to enter the war zone with the earliest contingents of NATO peacekeeping troops. Blewitt said today this would begin "as soon as it is safe to do so, hopefully within one or two or three days of their initial deployment."

Arbour said she had received excellent assurances to that effect from Gen. Wesley K. Clark, the supreme allied commander, at a meeting Monday at NATO headquarters in Belgium, and earlier from Lt. Gen. Mike Jackson, the British commander of the peacekeeping force.

"Depending on how it unfolds," Arbour said, "there will be a quick deployment of additional forensic experts on an exploratory mission" to survey sites of reported massacres and other atrocities committed against ethnic Albanians in Kosovo, a province of Serbia, Yugoslavia's dominant republic. Ethnic Albanian guerrillas began a serious push for an independent Kosovo last year, triggering the government crackdown that led to the 11-week NATO bombing campaign against Yugoslavia.

The United States, Britain, France, Canada and other countries have promised technical assistance and personnel -- ballistics experts and victim identification specialists, for example. But it is doubtful that these reinforcements will be in place in time to move in with the first peacekeeping troops. "We don't know how many [investigators] we'll have and when they can get there. We're going to have to go in with what we have," Blewitt said.

No more than two dozen tribunal employees are assigned to this investigation right now, and the panel operates under U.N. regulations that usually restrict the use of personnel offered by national police and legal agencies. Prosecutors in The Hague, where the tribunal is based, said investigators and their interpreters also need armed protection of suspected sites and security for the people sifting through the evidence, as well as transportation and accommodations. Heavy equipment needed by the tribunal to assist in exhumations is in Bosnia at present, uncovering evidence of war crimes from the 1992-95 war in that former Yugoslav republic.

Tribunal officials and nongovernmental humanitarian workers said today that immediate access is urgent to secure and seal sites of massacres, torture and detention, and to interview new witnesses while memories are fresh and evidence has not disappeared.

Blewitt said that at a minimum, tribunal investigators want to proceed "simultaneously" to seven places in Kosovo identified as scenes of systematic and large-scale executions in the tribunal's May 27 war-crimes indictment of Yugoslav President Slobodan Milosevic and four top political and military leaders. The indictment lists more than 340 victims who have been identified; most are men or boys who died at these sites in January, March and April.

"The downside of making anything public," Arbour said, referring to 42-page indictment, "is that you identify your centers of interest" to prospective legal defense teams of the indicted leaders -- and to military and police forces. But she and Blewitt said they expect that tribunal officials operating under the protection of NATO forces would find evidence of other atrocities.

Recent published reports in Europe and the United States asserted that Serb-led forces have been disposing the bodies of murdered civilians -- exhuming corpses from grave sites and transporting them to makeshift incinerators in mines, factories and garbage dumps in Kosovo. The reports have not been confirmed.

"Sometimes the most incriminating cases are based on tampering and interference," Arbour said. She said the early investigations will focus on concerted efforts to cover up crimes described by refugees, journalists and intelligence sources.

Arbour said she had talked with Clark and Jackson about obtaining access to maps of land mines planted by Yugoslav and Serbian forces and de-mining assistance for tribunal investigators -- particularly around mass graves and improvised crematoriums.

But the tribunal's need for de-mining assistance will have to compete with similar requirements by military forces entering Kosovo and returning refugees.