Top Pentagon officials complained yesterday that the United Nations is lagging in setting up a police force and civil administration in Kosovo, putting added strain on U.S. and other NATO peacekeeping troops in the Serbian province.

"We are concerned about the slow progress in establishing the United Nations mission in Kosovo to aid in the recovery process," Gen. Henry H. Shelton, chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee.

With only 600 of a projected U.N. staff of 5,000 in place, Shelton and Defense Secretary William S. Cohen, who testified at the same hearing, said the administration is pressing the United Nations to accelerate its efforts. But both men cited sluggish performance by the United Nations and other international institutions in managing earlier reconstruction programs in Haiti and Bosnia.

While a NATO-led force of more than 50,000 soldiers has been pouring into Kosovo to impose order after the withdrawal of Yugoslav troops last month, the United Nations is responsible for creating an interim government and fielding about 3,000 international police officers to help patrol the battered province until local police can be trained. But the United Nations has no standing constabulary corps and so must recruit police volunteers as well as civil administrators from member nations. The job, in turn, of training a new home-grown police force belongs to the Organization for Security and Cooperation in Europe, whose timetable also has slipped, Shelton said.

The Pentagon, which normally views police work and civil administration as non-military tasks, reluctantly agreed that U.S. and other NATO troops would perform them temporarily in Kosovo until the United Nations could get organized. But defense officials are eager to hand over responsibility to U.N. staff.

"There is no higher priority right now, I think, than getting a police force and a justice system established," Shelton said.

He expressed concern that the longer NATO troops engage in "police-type actions"--arresting lawbreakers and patrolling neighborhoods--the greater the risk that they will be perceived as taking one side or the other between Serbs and Albanians. He also said NATO lacked enough troops to keep a close watch on the entire province.

Shelton and Cohen said the risk of widespread violence in Kosovo is smaller than in Bosnia, where ethnic factions are more numerous and in closer proximity. So the faster the United Nations and the OSCE can set up in Kosovo, they said, the faster NATO troops can begin a phased withdrawal.

While insisting that U.S. troops will not be kept in Kosovo indefinitely, the Pentagon leaders said there is no timetable for withdrawing them.