WASHINGTON (CNN) -- The United States warned Yugoslav President Slobodan Milosevic that he will be held "personally responsible" if any harm comes to unarmed observers being sent into Kosovo to monitor Yugoslavia's troop pullback.

National Security Adviser Sandy Berger said Friday that a NATO rapid response team is being assembled in neighboring Macedonia to extract the observers if they come under attack.

"If anything happens to those monitors and verifiers at the hands of the Serbs, we know exactly where the address is in Belgrade," Berger said. "We have made it very clear to Mr. Milosevic that if any harm comes to our people or the international people, we will hold him personally responsible."

Berger did not elaborate on what actions might be taken against the Yugoslavs in the event of an attack.

Some 2,000 monitors from the Organization for Security and Cooperation in Europe are being deployed in the Yugoslav province of Kosovo to monitor Serb compliance with Milosevic's promise to Western powers to stop a seven-month crackdown on ethnic Albanian separatists there. Americans will make up part of the monitoring force.

The mission is also expected to serve as a deterrent to further fighting between Yugoslav forces and the guerrillas of the Kosovo Liberation Army. A respite would provide greater safety for ethnic Albanian refugees who want to return to their homes.

"It is extremely important in terms of deterrence because it will be difficult for either party, but in particular Milosevic, to re-engage in a massive military way without the international community being quickly alert to what he is doing," Berger said.

Reuters contributed to this report.