ELGRADE, Oct. 3 — The United States has accepted an offer by Serbia and Montenegro to send up to 1,000 combat troops and police officers to Afghanistan to join American forces there, senior Serbian officials and foreign diplomats said today.

The Serbian-Montenegrin force, which will have to be trained to function under American operational command, will be based in the Kandahar region near the Pakistani border, the officials said. The troops are expected to be ready for deployment by March. Afghan officials have not reacted to the plan so far.

Boris Tadic, the defense minister of Serbia and Montenegro, said at a news conference today that Liberia, Iraq and Afghanistan were discussed as possible destinations for Serbian troops and that "it is more likely that Afghanistan is the potential destination."

The deployment will be highly unusual. It raises the question of whether it will include Serbian troops or officers who may have been involved in committing atrocities against Muslims in either the war in Bosnia in the early 1990's or the more recent conflict in Kosovo. Officials said the United States military intended to vet all soldiers and police officers in the all-volunteer force.

In addition, the possibility that Serbian troops, who battled Muslims in Bosnia and in Kosovo in the Balkan wars of the 1990's, could be involved in combat operations against Muslims and in antiterrorist operations against members and supporters of Al Qaeda might be seen by both Muslims and non-Muslims as undesirable.

Finally, the Serbs were bombed for nearly three months by American forces in NATO's conflict with the then Yugoslavia over Kosovo in 1999 — and now they will be serving side by side with Americans.

Carla Del Ponte, the chief prosecutor at the United Nations war crimes tribunal in The Hague, was in Belgrade on Friday, reiterating previous demands that Serbia do more to cooperate in bringing war criminals to justice at the court. She insisted once again that one of the leading fugitives, the former Bosnian Serb military commander Gen. Ratko Mladic, was in Serbia.

Since Slobodan Milosevic, who is now on trial in The Hague, was ousted three years ago as Serbia's leader, the country's new rulers have sought ways to cooperate with Washington. Like leaders of other former Communist countries seeking acceptance by the West, they are keenly aware of the American need for troops in both Iraq and Afghanistan.

"I support the idea that our soldiers and the police force become a part of the military contingent in Afghanistan," the Serbian deputy prime minister, Nebojsa Covic, said in an interview with foreign journalists traveling in the Balkans with Richard C. Holbrooke, assistant secretary of state for European affairs under President Clinton. "I think it is a good thing to build up cooperation on a military level after so many years of misunderstandings, conflicts and confrontations. As you know, our soldiers and police forces have experience in fighting terrorism, and I hope that the allied forces can benefit from that experience."

The approval of NATO is not necessary for the deployment, since it would be part of the American-run postwar military operation in Afghanistan, not the NATO-led forces keeping the peace in Kabul.

Prime Minister Zoran Zivkovic of Serbia and Foreign Minister Goran Svilanovic of the federation of Serbia and Montenegro first made the offer to send peacekeeping troops to Condoleezza Rice, the White House national security adviser, and Secretary of State Colin L. Powell during a visit to Washington two months ago.

One official familiar with the offer said it came "out of the blue."

The United States Central Command, which is responsible for American military participation in Afghanistan, swiftly approved the proposal, but told the Serbs that the United States wanted infantry troops rather than lightly armed peacekeepers.

The American thinking was that the need for combat troops ready to take casualties in Afghanistan overrode political considerations about the wisdom of such a mission, and that in any case, the Serbs would probably be on their best behavior, officials indicated.

About two weeks ago, a delegation from the army and the gendarmerie, or national police force, visited the United States for what Mr. Tadic said today were "technical discussions in connection with possible participation" in a foreign mission.

Other officials said that the areas of responsibility and reporting channels were defined and that a Serbian liaison officer had been based at the Central Command headquarters in Florida. An American mission will travel to Belgrade shortly to assess the level of training and equipment of the troops and police officers, these officials said.

Mr. Tadic stressed, however, that the final decision to send troops had to be formally approved by the Defense Council, the Council of Ministers and the joint Parliament of Serbia and Montenegro. He is also said to be concerned that he might have to take highly trained troops out of southern Serbia, close to Kosovo, which since the 1999 war has been run by the United Nations and patrolled by foreign peacekeepers, to send them to Afghanistan.

According to press reports here, the Serbs originally proposed that Gen. Goran Radosavljevic, chief of the gendarmerie, head the Serb contingent.

But the general led teams against armed Albanians during the Kosovo war, and a number of human rights groups have charged that those Serbian teams committed atrocities against civilians. Human Rights Watch contends that members of these teams killed 41 ethnic Albanians in May 1999.

Officials familiar with the negotiations on the Serbian force insist that a commander like General Radosavljevic would be unacceptable, and that no decisions have been made on who will join or lead the Serb contingent.