The Reagan administration said yesterday that a proposal by Soviet leader Yuri Andropov to reduce the number of intermediate-range missiles in Europe is "unacceptable" because Moscow would still have a monopoly on such weapons "involving several hundred warheads" and would deny the United States "the means to deter that threat."

Andropov said he is willing to cut the number of new triple-warhead SS20 missiles deployed in the European areas of the Soviet Union to 162, the same as in the French and British nuclear arsenals.

The Soviets now have 333 SS20s--234 in Europe and 99 east of the Ural Mountains presumably aimed at Asia. Andropov did not say if the mobile missiles taken out of Europe would be dismantled or merely moved east of the Urals, and he did not offer to reduce the 99 SS20s already there.

In effect, U.S. officials said the Soviet proposal was nothing new and amounted only to moving 72 missiles from the European to Asian portions of the Soviet Union, with no guarantee that they would be destroyed or not moved back someday.

The official U.S. rejection was delivered by State Department spokesman John Hughes, who said in a statement that "we cannot accept that the U.S. should agree to allow the Soviets superiority over us because the British and French maintain their own national deterrent forces."

Hughes said the United States cannot agree that limits on these missiles should apply only in Europe and thus leave the Soviets "free to threaten our Asian friends" with them. He noted that because the 3,000-mile-range SS20s are mobile they also could be moved from Asia and into position to threaten Europe.

State Department and Pentagon officials, briefing reporters on condition that they not be identified, stressed that North Atlantic Treaty Organization allies remain firmly behind President Reagan's so-called "zero-option" plan presented at the Geneva arms talks.

This would eliminate all SS20s and about 300 older Soviet missiles. In return, the United States would not deploy 572 new U.S.-built Pershing II and cruise missiles in Western Europe beginning late next year to counter the Soviet weapons.

The officials said Andropov's proposal was basically a "repackaging" of earlier, informal Soviet proposals to limit missiles and bombers in Europe. The only difference is that the new proposal has a specific sub-ceiling of 162 missiles in the European region.

They stressed that in every Soviet version proposed at Geneva not one U.S. missile could be deployed, while the Soviets could keep perhaps even more than the 250 SS20s they had when the arms talks began a year ago.

The Pentagon official said he believes Andropov's proposal "is intended to produce a negotiation in the editorial pages of the United States and its allies . . . by creating the impression of movement on their part. I think the Soviets are hoping this will undermine support" for the allied decision to deploy new missiles barring an arms control agreement.

"I think they are wrong" in this hope, he said.

The official claimed Moscow has been knocked off balance by the general appeal of the zero-option plan. The forthcoming U.S. missile deployments, however, are extremely controversial among Europeans.

U.S. officials said the British force of 64 submarine-based missiles and the French force of 18 land-based missiles and 80 submarine-based weapons are sovereign and independent forces that cannot be negotiated away by the United States. They are meant to deter attack on those countries and are not part of the NATO deterrent force. For example, the British and French missiles might not be fired if the Soviets attacked West Germany.

The officials said the Soviet effort amounts to a public relations effort to "divide the alliance and separate the United States from its allies." If the United States had no new missiles in Europe while even part of the Soviet force was retained, they said, it would have "profound political and psychological consequences" in Europe by weakening the credibility of U.S. nuclear protection for Europe.

"The Soviets have got to understand," the State Department official said, "that the key to resolving the missile issue lies in Geneva in serious negotiations and not in trying to influence public opinion." The Soviets, he said, would like to derail the NATO commitment to deploy new weapons without paying anything for it.

Despite the generally negative tone of their briefing, the officials said that they are not pessimistic about an eventual negotiated agreement but that chances are good only if the allies proceed toward the scheduled deployment.

The officials also denied that their tone contrasted to Reagan's recent statement that the Soviets are negotiating seriously in Geneva. They said the president was referring to talks on reducing strategic intercontinental-range missiles, not the shorter-ranged ones in Europe.

The strategic arms talks involve weapons that both sides have in large numbers; in intermediate-range missiles, the Soviets have virtually a monopoly over the United States.