The Soviet Union has expressed serious reservations about holding the next summit meeting of President Reagan and Soviet leader Mikhail Gorbachev in late June as proposed by Washington, and has suggested September as a possible alternative, according to State Department officials.

Officials described the Soviet reservations, conveyed through Ambassador Anatoliy Dobrynin, as short of a definite rejection of a June summit in Washington and said the September suggestion was similarly informal.

However, there is no doubt that the preference expressed by Dobrynin for a later date has made a June summit much less likely than it seemed a few weeks ago, in the view of U.S. officials.

A White House official said the likelihood as of now is that the summit will be held in early September.

Late September or October is not likely to be acceptable to the United States. Secretary of State George P. Shultz and others in the administration are reported to be determined that the next Reagan-Gorbachev meeting not be held close to the Nov. 4 congressional elections because of concern that U.S.-Soviet relations could become embroiled in U.S. politics.

In their joint communique last November, Reagan and Gorbachev agreed to meet again "in the nearest future," with details to be worked out through diplomatic channels. Reagan told a joint session of Congress Nov. 21 that Gorbachev would come to the United States in 1986 and that he, Reagan, would visit the Soviet Union in 1987.

Reagan and Gorbachev have exchanged videotaped New Year's greetings, which will be broadcast today in the United States and the Soviet Union. Reagan's message, a text of which was obtained by The Washington Post, focuses largely on the "good beginning" made at the Geneva summit.

In a carefully worded reference to U.S. concerns about human rights, Reagan will tell the Soviet people: "Our democratic system is founded on the belief in the sanctity of human life and the rights of the individual -- rights such as freedom of speech, of assembly, of movement and of worship."

Reagan also delicately broached the controversial subject of strategic defenses against nuclear missiles by noting: "Both the United States and the Soviet Union are doing research on the possibilities of applying new technologies to the cause of defense. If these technologies become a reality, it's my dream to one day free us all from the threat of nuclear destruction."

The idea of a June summit, though discussed by high U.S. officials with journalists at Geneva, was not formally proposed to the Soviets until early last month. The thinking behind the June proposal was to "sustain the momentum" in U.S.-Soviet relations, to take advantage of good weather in Washington and to avoid running close to the fall elections, according to official sources.

The Soviet reservation is said to be buttressed by concern that insufficient time will have elapsed for the two nations to have moved toward substantive accords, especially in the important field of arms control.

One administration official, who describes himself as highly critical of the Soviets, expressed the view that Moscow wants to schedule the summit as close as possible to the U.S. elections in order to put maximum domestic pressure on Reagan to make concessions in the interest of an amicable and successful meeting.

According to informed sources, Reagan told Gorbachev in Geneva that he hoped the Soviet leader would see some of the United States following official meetings in Washington. A brief U.S. tour, perhaps three or four days, after Reagan-Gorbachev meetings in Washington is considered likely, whenever the summit takes place.

In 1959, Soviet leader Nikita Khrushchev made an eight-day tour of the country after two days of meetings with President Dwight D. Eisenhower and before a final three-day visit to Camp David, Md.

The timing of the next Reagan-Gorbachev summit could affect the dates of an earlier exchange of visits between Shultz and Soviet Foreign Minister Eduard Shevardnadze, officials said.

Shultz and Shevardnadze reportedly reached an informal "understanding" in Geneva to hold discussions, probably a visit here by Shevardnadze followed by a Shultz trip to Moscow, in preparation for the next meeting of Reagan and Gorbachev.

If the Reagan-Gorbachev meeting is to be held late in June as proposed by Washington, the preparatory sessions will have to get under way quickly, probably before the important Soviet Communist Party Congress late in February. But if the summit is postponed, it seems more likely that the first Shultz-Shevardnadze preparatory meeting will be put off until the spring.

In-depth discussion of one or two regional conflicts involving the nuclear superpowers is expected to be a major feature of each of the preparatory meetings, according to State Department officials. The current U.S. thinking is that Afghanistan and southern Africa present the greatest opportunities for fruitful discussion in the initial preparatory meeting, officials said.