President Reagan and Soviet President Leonid Brezhnev have exchanged messages in writing four or five times this year, State Department sources said yesterday, but there is little likelihood of an early meeting to exchange ideas face to face.

State Department spokesman Dean Fischer and other officials went out of their way to discourage talk of an early summit meeting following Reagan's statement to reporters in California Thursday. Reagan said he had suggested to Brezhnev in correspondence "that maybe we might sit down sometime" in the interest of peace.

Reagan's remark does not reflect a new policy or a new phase of policy, Fischer said. He said Reagan has called for an active Soviet-American dialogue "at all levels, including the summit," but noted that Reagan also had said that any summit meeting should be carefully prepared.

Brezhnev publicly proposed a meeting with Reagan in his speech Feb. 23 to the 26th Congress of the Soviet Communist Party. At that time, the Soviet leader said such a meeting would be "the crucial link" in Soviet-American dialogue.

Reagan responded three days later, in a White House welcoming ceremony for British Prime Minister Margaret Thatcher, by saying that "we certainly have an interest in pursuing a serious, constructive dialogue with the Soviets on the issues which divide us" and adding that the summit proposal "needs to be carefully studied."

Answering questions yesterday, Fischer said a summit invitation is not available to Brezhnev prior to "advance preparations" that would make such a meeting successful. He declined to specify these preparations but seemed to hint that a shift in Soviet conduct would be necessary by saying that "we've repeatedly made clear an improved relationship has to be based on restraint and reciprocity."

Reagan also told reporters at his California ranch Thursday that "I have asked that we the U.S. and Soviet Union meet to legitimately discuss the reduction of armaments on both sides, particularly in strategic weapons."

Several administration officials expressed uncertainty about what Reagan meant, since government positions on a new strategic arms agreement remain in an early stage.

Secretary of State Alexander M. Haig Jr. is expected to mention the subject of strategic arms in his planned talk with Soviet Foreign Minister Andrei Gromyko at the United Nations in the latter part of September. But U.S. officials said the administration is far from ready for concrete talks.

At the State Department yesterday, the administration's chief strategic arms negotiator, retired general Edward L. Rowny, took the occasion of his swearing-in ceremony to speak of some imposing requirements of a new strategic arms agreement.

Rowny, who had been the Joint Chiefs of Staff representative at SALT negotiations with the Soviets for six years, resigned from military service two years ago in order to oppose the SALT II treaty negotiated by the Carter administration.

Rowny said he took this step because, in his view, SALT II was "neither equitable nor verifiable." In general terms, he suggested that the following would successfully meet those tests:

"Equality in agreements does not mean equal number of launchers alone, but also means equality in the destructive potential of the weapons themselves."

This statement apparently reflects internal proposals that the administration should aim for large-scale reductions in U.S. and Soviet missile throw weight (lifting power), in which the Soviets are far ahead of the United States, and numbers of warheads, in which the United States is slightly ahead. Large cuts in deliverable explosive power would go much further than the Soviets have been prepared to go previously.

"Secondly, any agreement entered into must be verifiable. This will be increasingly difficult to achieve in the future solely through national technical means primarily faraway monitoring stations and spy satellites ," Rowny said.

Rowny is reported to be proposing "cooperative measures" to be worked out between the two sides to verify limits on such weapons as cruise missiles and complex weapons systems of the future.

In another arms control development, the State Department said it is exploring with several countries the concept of a "nuclear weapons free zone" in the Middle East.

Fischer indicated that such a zone might be modeled on the 1974 Egyptian-Iranian proposal, which has been consistently backed by the United States and most other countries at the United Nations, banning the acquisition of nuclear weapons by states in the area and the stationing of such weapons there by the big powers.

Israel, which is believed to possess nuclear weapons in component form, has abstained from voting at the U.N. on the Mideast nuclear weapons free zone and is believed unlikely to accept it.