Soviet leader Mikhail Gorbachev said today that the Soviet Union would back establishment of a zone free of chemical weapons in Europe if the United States supported the proposal.

In a meeting with Johannes Rau, vice chairman of West Germany's center-left opposition Social Democratic Party and the party's likely next candidate for chancellor, Gorbachev said that if such a zone were created the Soviet Union would "guarantee and respect" it, the Soviet news agency Tass said.

A White House spokesman later rejected the idea. Spokesman Edward Djerejian said the United States seeks "a comprehensive, verifiable ban" on chemical weapons, and "until such a ban is negotiated, the U.S. must maintain a credible deterrent against Soviet use of chemical weapons."

"The facts are that the U.S. has for the past 16 years unilaterally refrained from any chemical weapons production. But obviously what we've been faced with is a lack of Soviet restraint. They have continued chemical weapons production during this period," Djerejian said.

[A White House official who asked not to be identified said the United States has no plans to place chemical weapons in foreign countries.]

Gorbachev's expression of support for such a zone during his meeting with Rau is viewed here as part of a tendency by the Kremlin to support causes popular with the Western European Social Democratic parties. The campaign, diplomats here said, is likely to intensify as the November summit meeting between Gorbachev and President Reagan nears.

Both West Germany's Social Democratic Party and the East German government favor a chemical-weapons-free zone, which was originally proposed in a commission chaired by Olof Palme, Social Democratic prime minister of Sweden.

West European diplomats said that the U.S. allies in Europe, especially the West Germans, are eager for at least some movement in some area of arms control to result from the summit talks. The diplomats said that chemical weaponry is one possible area that would have important political overtones in West Germany.

Vice President Bush also spoke of prospects for agreements on chemical weapons earlier this week, but not in the context of a zone as mentioned by Gorbachev.

Tass said the Soviet Union favors the implementation of a "nuclear-free corridor" along the border between the Warsaw Pact countries and the North Atlantic Treaty Organization countries.

Soviet officials here have stressed the importance of reaching some agreement on Reagan's Strategic Defense Initiative, or "Star Wars" research plan on a space-based antimissile defense system, during the summit talks. The Soviet Union is expected to encourage West European leaders to pressure the White House to concede to an SDI agreement, western diplomats here feel.

Rau said in a press conference today that Gorbachev also criticized West Germany's speed in supporting Reagan's SDI plan, which is heavily debated among the U.S. allies in Western Europe.

But Rau, who is expected to challenge Chancellor Helmut Kohl in 1987 elections, told Gorbachev that his party was opposed to the initiative, and that there were also differences of opinion about it within the Kohl coalition government.

Gorbachev is scheduled to meet in Paris in early October with French President Francois Mitterrand, who also has criticized SDI.

Meanwhile, Gorbachev, in a speech televised tonight but given two weeks ago to party workers in Kazakstan, defended the country's agricultural plan and stressed the importance of meeting agricultural production goals and improving social conditions in the countryside.