The Carter administration yesterday cautiously welcomed reports that Moscow is willing to discuss limiting nuclear missile forces in Europe, but worried that the Soviets may seek to include in the negotiations some other U.S. weapons systems that the administration would rather not discuss.

The Kremlin's new stand was revealed in some detail yesterday in Bonn.

West German Chancellor Helmut Schmidt reported that, during his visit to Moscow last week, Soviet President Leonid I. Brezhnev agreed to drop the major condition that thus far had prevented any discussion on limiting both Sovietand Western missile forces.

Moscow, Schmidt said, would no longer insist that before the talks start the North Atlantic Treaty Organization (NATO) must rescind its plan to install, beginning in 1983, new U.S. missiles in Europe.

The U.S. missiles are meant eventually to counterbalance some 200 Soviet intermediate-range SS20 missiles already deployed and aimed, for the most part, at Western Europe.

But Schmidt also relayed that Brezhnev suggested that any talks should also include the so-called U.S. "forward-based systems," which in the language of arms control, means the hundreds of U.S. warplanes based on Navy aircraft carriers and at airfields around Europe and possibly some U.S. missile-firing submarines in European waters.

The Kremlin has always tried to include these planes, some of which can reach the Soviet Union with nuclear bombs, in previous arms negotiations, and the United States has thus far successfully kept them out.

Thus, while the Kremlin's new offer seems to have some appeal in trying to limit missiles, it may raise new challengesto the U.S. air fleet overseas that could be a serious complication.

U.S. officials said they view landbased missiles as the biggest problem to be negotiated, certainly in the first efforts, and are not at all sure they want to get intoaircraft at any point.

"If they're just trying to replace one unacceptable pre-condition with another unacceptable one," said one official, "then we have problems."

Top Carter administration specialists said yesterday that they will be making contact with Soviet officials "fairly soon" to seekclarification of exactly what Moscow has in mind, though itis not yet decided how or when that contact will be made.

The Schmidt-Brezhnev discussions clearly sparked a lot of activity here within the administration. There was also a special NATO meeting in Brussels yesterday, to begin developing an alliance position, at which German officials outlinedthe Soviet stance.

Privately, some administration officials said they certainly would put the new Soviet arms control feeler in the category of attempts by Moscow to "look peace-loving and draw attention away from Afghanistan." Yet these officials added that they do not mean to demean the potential positive aspects of the proposal.

"Obviously, the fact that they dropped their pre-condition is important, and wedon't want to pooh-pooh that even though it should never have been a pre-condition to begin with," one official said.

When NATO, last December, approved the plan to install theU.S. missiles, it coupled that with an offer by the United States to negotiate joint limitations on these weapons during the three years it would take to field them. In January, Moscow flatly rejected the NATO offer.

Brezhnev's apparent change of heart "came a lot earlier" than the United States expected, officials said. But it is uncertain whether it is because Moscow wants to take the heat off the Afghanistansituation or because, as U.S. officials hope, that Brezhnevwas convinced that NATO would stick by its deployment decision.

The White House is also clearly hoping that its NATOallies will interpret Moscow's new moves as confirmation that the United States was right in insisting that the West must go ahead and beef up its arsenal for any future talks to produce a realistic arms balance.

Thus far, only West Germany, England and Italy have agreed to accept the new U.S. missiles on their soil. Belgium and Holland continue to hold out, and what the effect in those two countries will be of the new Soviet moves is uncertain.

Though Moscow also dropped its condition that the pending U.S.-Soviet strategic arms limitation treaty (Salt II) be approved by the Senate before negotiations begin on these shorter range missiles, Brezhnev made it clear that ratification of SALT II would be necessary before any European missile pact could be concluded.

This is not a problem for the White House, officials say,because the Carter administration remains committed to getting SALT ratified, even though it has done little to accomplish that due to the Soviet invasion of Afghanistan and the U.S. election.