The Reagan administration's chief arms negotiator said yesterday the major obstacle to a U.S.-Soviet agreement eliminating medium-range and short-range nuclear missiles could be overcome outside of the Geneva talks.

But Ambassador Max M. Kampelman reiterated that the United States would not resolve the issue in bilateral negotiations.

The Soviets have called the 72 West German Pershing IA missiles armed with U.S. nuclear warheads the chief impediment to a U.S.-Soviet treaty. The Soviets have demanded their removal in exchange for the destruction of all Soviet missiles of similar range in Europe and Asia under the so-called global double-zero proposal.

A way around the impasse might be to retire the missiles when they become obsolete in a few years, Kampelman said on NBC News' "Meet the Press."

"It's obviously an option that we've already been discussing with the Soviets," Kampelman said when asked if such a compromise could be reached. "An option means we've been trying to examine it, what its implications are."

The United States has held firmly to the position that the warheads are exempt from the negotiations because the missiles were sold to Bonn under longstanding cooperative arrangements.

In a later interview, Kampelman said the administration's position does not rule out a separate agreement involving Germany or NATO. If the Soviets advanced a compromise proposal, "we would take it up with our allies," he said.

Soviet deputy arms control negotiator Alexei A. Obukhov, who appeared opposite Kampelman on "Meet the Press," said the Soviets would consider such a proposal seriously, but only if the United States suggested it first.

Obukhov called such a proposal "a hypothetical situation" but said, "We will listen to what Ambassador Kampelman is going to propose, we will study, and we will give our answer."

Obukhov's comments reflected greater flexibility than statements by other senior Soviet arms control officials in an interview in Moscow last week with Washington Post correspondents.

The Soviets doubt that the American warheads on the German missiles are approaching obsolescence and require assurance that the Pershing IAs will not remain a threat, Viktor Karpov, chief of the Soviet Foreign Ministry's arms control department, said yesterday on CBS News' "Face the Nation."

Kenneth L. Adelman, departing director of the U.S. Arms Control and Disarmament Agency, said on the CBS program that the Soviets are using the Pershing IAs as a ploy.

"I think the Soviets are just engaged in their latest bluff," he said.