MOSCOW, OCT. 26 -- The intensive U.S.-Soviet arms discussions here last week showed that the dispute between Kremlin leader Mikhail Gorbachev and President Reagan over the "Star Wars" program, boils down to three key areas, western and Soviet arms experts said.

Diplomats here said these areas appear to be rooted in fundamentally different approaches to arms control by Reagan and Gorbachev and can probably only be resolved in a working meeting between the two, if at all.

Moscow's strongest objection is to Reagan's insistence on the right eventually to deploy an antimissile defense shield in space in spite of any interim arms accords the two sides achieve, the specialists said.

U.S. and Soviet negotiators also differ over which components of the Strategic Defense Initiative -- the formal name of Star Wars -- the United States can test in space under the terms of the 1972 U.S.-Soviet antiballistic missile treaty. The third area of disagreement is over how long the two countries should abide by the 1972 agreement's restrictions on development, testing and deployment of future antiballistic missile systems.

After two days of talks here late last week, Gorbachev refused to set dates for a summit meeting with Reagan in Washington, citing the lack of progress in negotiations over Star Wars and proposed cuts in U.S. and Soviet long-range offensive missiles.

Gorbachev's objections, climaxing a four-year-old dispute between Moscow and Washington over Star Wars, appear to reflect a basic difference with Reagan over the goals of arms control. "It's not so clear," Secretary of State George P. Shultz said in reference to a conversation with Gorbachev on space defense, "that our objectives are congruent and therefore it seems more difficult for us to find the way."

During two years of negotiations in Geneva, U.S. and Soviet experts have only superficially narrowed the interpretive gap over Star Wars between the two sides, western diplomats said.

And yet, senior U.S. and Soviet officials also disagreed here publicly over whether a working summit or further talks in Geneva are the best way to resolve the remaining differences.

Shultz stressed in a speech and a press conference here that a summit could be a venue for exploring some solutions.

In a speech last Thursday, however, Soviet Foreign Minister Eduard Shevardnadze stressed the need for negotiators in Geneva to iron out the differences. The Soviet Union is submitting new proposals in Geneva this week for deep cuts in strategic weapons.

The Soviets view their new proposals on intercontinental-range missiles, offered by Gorbachev in talks Friday with Shultz, and their agreement to another summit with Reagan, as bargaining chips with which to negotiate a compromise with the Reagan administration over Star Wars.

In his press conference Friday, Shultz objected to the Kremlin's linkage of deep cuts in strategic weapons to limits on Star Wars as "not warranted," although Washington is anxious to negotiate reductions in Soviet land-based strategic missiles.

Moscow has now shifted the negotiations on limiting space defense research to Geneva, despite charges from both Soviet and U.S. officials that each side's Geneva negotiators have been dragging their feet in the space weapons talks.

In an apparent attempt to break the longstanding disagreement between the sides over the components of defensive weapons systems that could be tested in space, Shevardnadze proposed, during a trip to Washington last month, that the two sides identify what devices might be acceptable for deployment in space. Soviet negotiators in Geneva later submitted a list of characteristics for devices Moscow would accept in space.

The move was viewed widely as a drastic evolution in Moscow's original position that the ABM treaty allowed no deployments in space.

Still, in a press conference on the eve of his Moscow trip, Shultz said the new Soviet proposal was probed thoroughly in Geneva and "the more we try to pin it down, the less there seems to be there."

The dispute between the two sides over the list in Geneva was most likely rooted in a basic U.S.-Soviet dispute over whether the ABM treaty should be adapted to put limits on what can be tested and deployed in space. The United States is against it. Following last week's talks here, Shevardnadze complained that the U.S. delegation -- including chief arms negotiator Max Kampelman -- "did not manifest a readiness, on a businesslike and constructive basis, to discuss questions relating to preserving the ABM treaty."

More central to the U.S.-Soviet differences over Star Wars than the terms of testing under the treaty, however, is a Reagan administration commitment to the right to deploy a space shield after giving the required notice of intention to withdraw from the treaty.

Shultz assured journalists that Reagan has no intention of forgoing the right to deploy. "The president will not -- and none of his advisers have anything but full support for him in this -- he will not give up the ability of the United States to pursue the research necessary and for that matter be prepared if the research pans out to move ahead with defending ourselves against ballistic missiles."

The position confounds the Soviet attempt to prevent a situation where deployment of an antimissile shield in space is necessary. Moscow is thought to be worried about other U.S. technological advances that would result from Star Wars research, and the technical and financial challenge the Soviet military would face in overcoming such a shield. Instead, Soviet diplomats argue, reductions of strategic weapons on both sides should be deep enough after a few years that a space shield would become irrevelant.