U.S. special envoy Paul Nitze said today that "significant differences" divide the United States and the Soviet Union in their approach to the new arms control talks decided upon earlier this week in Geneva.

Nitze, here to brief the West German government on the outcome of the talks, said the two superpowers had particular differences over the relationship between the three sets of talks that are expected to begin probably in March.

The Reagan administration, he said, is prepared to carry out separate arms control accords, in different stages, during the forthcoming negotiations on nuclear and space weapons with the Soviet Union.

Nitze said the United States "saw no reason" why an agreement worked out in one of three areas to be negotiated -- strategic nuclear arms, medium-range nuclear missiles and space weapons -- could not be implemented ahead of the others. But he added that Moscow's position was "not quite the same."

[In Moscow, the Soviet news agency Tass issued an apparent warning that progress must be made in all three sets of talks, Reuter reported. Tass said the ruling Politburo, after a briefing on the Geneva talks by Foreign Minister Andrei Gromyko, had "stressed that only the strict observance during the forthcoming negotiations of the reached agreement in all of its parts can ensure real progress."]

The communique issued Tuesday at the end of the talks between Gromyko and U.S. Secretary of State George P. Shultz used deliberately ambiguous language on the question of how closely the three sets of talks will be linked:

"The sides agree that the subject of the negotiations will be a complex of questions concerning space and nuclear arms, both strategic and intermediate range, with all the questions considered and resolved in their interrelationship."

A member of the U.S. delegation told reporters that the relationship between the talks was "fuzzy," and Shultz, at a press conference after the communique was issued, said "it will have to be seen when something emerges from one of the groups . . . the extent to which the relationship would have an effect on whether that agreement would be brought forward and finalized."

At issue behind the two sides' maneuvers over the degree of linkage in the upcoming negotiations are their differing views of the question of space weapons, underscored in statements by Gromyko and White House national security adviser Robert McFarlane on Wednesday.

"The Soviet side particularly stressed the importance of preventing the militarization of outer space," Gromyko said in a reference to President Reagan's Strategic Defense Initiative, designed to establish a protective shield against offensive missiles and popularly known as "Star Wars."

In London, where he briefed British Prime Minister Margaret Thatcher on the Geneva talks, McFarlane said that it would take five to 10 years of research to determine whether a Star Wars missile defense was workable, and that any agreement to limit such research before then was "very much in doubt" because of the difficulties of verifying what was being done in U.S. and Soviet laboratories.

The Soviet Union's insistence on a package deal involving all three fields is but one of what Nitze called "significant differences" dividing the superpowers in their approach to new arms control talks.

Speaking at a news conference after meeting with Chancellor Helmut Kohl and West German government ministers, Nitze said the United States intended to seek "radical reductions in nuclear weapons" in the forthcoming talks.

But he stressed that the western alliance must maintain negotiating pressure on the Soviet Union by continuing with the deployment of 572 Pershing II and cruise nuclear missiles in Western Europe until an eventual arms pact restricts or eliminates them.

Nitze noted that the successful outcome of the Shultz-Gromyko talks was "in no small part due to the active support and solidarity of our allies." He said the West German government viewed the results accomplished at Geneva as "very favorable indeed" and underscored U.S. willingness to maintain close consultations with the allies during the course of the negotiations.

Nitze came to Bonn from Belgium and will visit the Netherlands on Friday. Both of those countries have wavered in their commitments to deploy 48 cruise missiles each under NATO's five-year deployment plan.

Britain, Italy and West Germany began stationing the missiles on their territories 13 months ago, prompting the Soviet Union to break off previous negotiations on strategic and intermediate-range nuclear weapons.

Moscow's emphasis on the linkage among the three negotiating areas appears to be rooted in its desire to exploit potential friction between the United States and its European allies once the negotiations begin, U.S. and West German officials said.

The Geneva talks call for the two delegations to split into three subgroups that will negotiate in an interconnected fashion the three areas of nuclear and space weaponry.

Under the new negotiating format, the officials said it was highly conceivable that the Soviet Union might try to drive a wedge within the western alliance by seeking to "hold hostage" any agreement limiting medium-range nuclear missiles in Europe until it gained more favorable terms on intercontinental missiles or space-based weapons.

Moscow as well as the European allies have expressed concern about the possibility that Reagan's Star Wars program could have a destabilizing impact on the strategic nuclear balance.

At his press conference, Nitze indicated that the United States had been unable to persuade the Soviet Union to accept its position that the two governments should not impose a "self-denying rule" that would block early implementation of arms control measures in the interests of both superpowers.

U.S. officials said later that they did not expect this conflict to delay the opening of negotiations. Rather, the problem was expected to emerge once the talks are underway.

"We will fight over it as soon negotiations get moving," an American diplomat said. "The Soviets will hold out for a complete package, and we will try to break it into smaller bites."

Nitze, who served as chief U.S. negotiator at the Geneva talks on intermediate nuclear missiles, said he did not think the Soviet Union had altered its demand that the independent nuclear deterrent forces of France and Britain be included in any agreement. The Soviet view, rejected by the United States and its allies, proved to be one of the major obstacles toward an agreement on medium-range missiles in Europe.