The United States and the Soviet Union have reached a tentative agreement on the time and place for a summit meeting between President Reagan and Soviet leader Mikhail Gorbachev, according to diplomatic sources here.

The proposed meeting would be held in Geneva in the second half of November, the sources said.

Settling the issue of time and place solves the main procedural problems for the summit, which was first proposed by Reagan in a letter to Gorbachev in March when the new Soviet leader took office.

[U.S. officials in Washington did not deny reports that a tentative date and time for the summit have been set. But they stressed that no final agreement has been made. "The two sides are still working on a place and on timing," said a State Department spokesman. "No agreement has been reached."]

Sources here said a final decision to proceed with the summit still depends on the events of the next four months, in particular on progress at the U.S.-Soviet arms talks now continuing in Geneva.

The U.S. Embassy here refused comment on the report of a preliminary agreement on a summit, as did officials at the Soviet Foreign Ministry.

The likelihood of a summit between the leaders of the two superpowers became greater this spring when Gorbachev succeeded the late Konstantin Chernenko. In the letter carried here by Vice President Bush to Chernenko's funeral, Reagan specifically invited Gorbachev to Washington.

Gorbachev, answering Reagan's letter, reportedly said he favored "the idea of a meeting," but indicated that a time and place still had to be agreed upon.

Since then, both sides have stuck to the line that an agreement to meet had been reached in principle, but that settling the final details required further discussions by the two countries' diplomats.

A meeting in Vienna last month between Secretary of State George P. Shultz and Soviet Foreign Minister Andrei Gromyko reportedly did not move the issue forward, according to western diplomats here.

American industrialist Armand Hammer reported after a meeting with Gorbachev two weeks ago that the Soviet leader had said that "to have a meeting, well, something has to be accomplished at such a meeting."

However, in recent weeks, western diplomats here have expressed increasing confidence that a Reagan-Gorbachev summit would take place.

Soviet officials and diplomats see developments at the negotiating table in Geneva as the key to a summit, particularly in light of the tough stance taken by Gorbachev in a recent speech.

During a visit to the Ukrainian city of Kiev this week, Gorbachev suggested that the Geneva talks might collapse unless the United States takes a "more reasonable stand."

Gorbachev said the Soviet Union would have to "reassess the entire situation" if the Americans continued a military buildup while "marking time" at Geneva.

The evolution of U.S.-Soviet relations, particularly in the field of arms control, is likely to determine the substantive agenda of any summit. U.S. officials at one point were describing their concept of the meeting as a "get-acquainted" session, or an opportunity for broad exchanges of views.

The plans so far are still preliminary and subject to change, sources said. But the agreement on time and place indicates a willingness on both sides to proceed in the direction of a summit, they said.

When Reagan first invited Gorbachev to Washington, U.S. officials said that the Soviets were due for a visit to the United States. The last time a Soviet leader came to Washington was in 1973, when Leonid Brezhnev met there with then-president Richard M. Nixon. Since then, American presidents have traveled outside the country four times for summit meetings with Soviet leaders.

In April, reports circulated that Gorbachev might go to New York in September for the opening of the 40th session of the United Nations General Assembly. It was widely assumed that Gorbachev would only go to New York if he planned to go on to Washington for a summit.

That plan, given credibility by the editor of the Communist Party newspaper Pravda in an interview April 22, was declared dead last week when senior U.S. officials confirmed that the Soviets had said officially that Gorbachev would not attend the U.N. session.