Eight Soviets proposed by Moscow to inspect U.S. missile sites under the new medium-range missile treaty have been rejected because the government believes they are spies, a U.S. official said Friday.

The eight were among hundreds of prospective monitors submitted by the Soviets to conduct ground inspection of American facilities. An equal number of U.S. monitors will be assigned to make sure the Soviets do not violate the treaty to scrap all U.S. and Soviet missiles in the range of 300 to 3,600 miles.The U.S. official said seven of the rejected Soviets had been proposed for surveillance of the Hercules rocket plant in West Valley City, Utah, and the eighth as a short-notice monitor elsewhere.

Under the treaty, both sides have the right to veto prospective inspectors without giving an explanation. The process is comparable to the peremptory challenge of prospective jurors in American trial courts.

Kendell Pease, spokesman for the U.S. On-Site Inspection Agency, declined to discuss the exchange of lists of prospective monitors between Washington and Moscow.

"The specifics of what was submitted and was returned is part of the privileged communication between the two countries and it would be inappropriate to get into the specifics of it," he said.

Under the treaty, the Soviets are permitted to send three groups of monitors. One is to patrol the Hercules facility to make sure production of Pershing rockets is not resumed. The missile is banned under the treaty signed last year by President Reagan and General Secretary Mikhail S. Gorbachev.

A second group will make short-notice inspection of other U.S. facilities, while the third are air crews used to ferry inspectors to the United States.

The Los Angeles Times reported the eight had been rejected during a screening process before 22 Soviet treaty inspectors arrived earlier this month, and the Soviet Union was not known to have complained about the rejections.

The Soviets' choice of the eight was seen by U.S. officials as evidence that the KGB intelligence agency and its military counterpart, the GRU, have not curbed their activities despite a warming in U.S.-Soviet relations, the newspaper reported.

The proposed inspectors had been linked to Soviet intelligence activities in the past, but not necessarily in the United States, the Times said.

None of the U.S. inspectors was rejected by the Soviets, the Times said.

Under the intermediate-range nuclear forces treaty, inspectors who are cleared may visit designated missile facilities in the host country and verify that the treaty's provisions for the elimination of all medium-range missiles are carried out.

U.S. counterintelligence officials consider the Hercules plant in Utah the facility most susceptible to technical and human intelligence gathering barred under the missile treaty, the Times said.

"The Soviets have (listening) platforms and agents on the East Coast and the West Coast, but none in middle America," an official told the Times. "We want to keep it that way."

Meanwhile, U.S. experts have arrived at a Soviet missile base in the Far East, a Soviet newspaper reported Friday. The U.S. group will have 24 hours at the Novosysoyevka base to examine shorter-range SS-12 missiles to be destroyed under the treaty, Stroitelnaya Gazeta said.