President Reagan and Soviet leader Mikhail Gorbachev are expected to agree next week to establish regular U.S.-Soviet consultations, including future summit conferences, that will give their Geneva meeting a measure of success even though it may not narrow their differences on nuclear arms control and other major issues.

U.S. officials furnished this assessment as last-minute messages were exchanged yesterday by Washington and Moscow and as negotiations on bilateral aviation issues were extended in the drive for additional accords.

"The results of the meetings will be a clear sign that the process of dialogue between the two nations has been restarted," said an official familiar with presummit diplomacy between the two capitals and plans for next week's events. "In this sense, the meetings are already guaranteed to be a success."

As Reagan and his aides prepare to fly to Geneva today, a major imponderable is the chemistry that will emerge from the potentially volatile mixture of a 74-year-old anti-Soviet U.S. president and a 54-year-old ideologically minded Soviet Communist Party chief.

A senior U.S. official said he expects that Gorbachev will not be as combative toward Reagan, who is a chief of state, as he was in his recent Kremlin meeting with Secretary of State George P. Shultz and White House national security affairs adviser Robert C. McFarlane.

But neither Reagan nor Gorbachev has participated in a business meeting with a leader of the rival superpower, which adds to the uncertainty of their encounter.

Another unknown factor here is whether Gorbachev will be bringing new gestures or concessions in order to display Soviet good faith and flexibility. Moscow's decisions to resolve 10 humanitarian cases of interest to the United States, which became known yesterday, are seen as such a signal, and officials say there could be more.

Some senior U.S. officials have been expecting the Soviets to make more moves to improve the atmosphere since the last few minutes of the last official meeting involving Shultz and McFarlane in Moscow Nov. 5.

After two days of unproductive sessions, Soviet Foreign Minister Eduard Shevardnadze surprised the U.S. team by asking that both sides "keep working" to make sure the summit meeting is "well prepared" so the world will see it as positive that leaders of the two countries have a healthy exchange.

Some U.S. participants took Shevardnadze's statement as a hint that Moscow would be more forthcoming in the days leading to the summit and would take pains to see that the meeting is seen as a success.

This positive, though vague, statement as Shultz prepared to leave Moscow may have accounted for Shultz's unusually ebullient demeanor even after a news conference in which he announced no progress in narrowing "deep differences" on major issues.

As of yesterday, this was the outlook in administration quarters for the main questions on the Reagan-Gorbachev agenda:

*Some progress is possible but none is certain on the central issues of arms control, the offensive nuclear systems and space defense systems covered by the Geneva nuclear and space talks.

The two sides have been unsuccessful in reaching an understanding to break the stalemate in the Geneva negotiations, and the likelihood is that Reagan and Gorbachev will be unable to do so.

A general statement of "guidelines" or objectives to spur the Geneva arms negotiators is under discussion, but it is still uncertain that an agreement can be reached. If no agreement is achieved, Reagan and Gorbachev might announce that they have issued separate -- and differing -- guidelines to their negotiators.

*A statement pledging U.S. and Soviet efforts to curb the proliferation of chemical weapons is expected. This is likely to be the charter for bilateral cooperation in this increasingly serious problem, supplementing a U.S. effort with advanced western industrial nations.

*No agreement is likely at the summit on extending the mutual policy of "not undercutting" the unratified SALT II agreement. The Soviets have asked for a one-year extension. Reagan is willing to continue the "no undercut" policy but is not willing now to commit himself to any time period.

*No agreement on settlement of major regional disputes, such as Afghanistan, Nicaragua, Angola, Cambodia, Ethiopia, the Middle East or southern Africa, is expected.

Earlier this fall there was hope in the State Department for Soviet movement toward a negotiated settlement of the war in Afghanistan. But this now seems unlikely at the summit.

*An agreement is expected to establish regular U.S.-Soviet consultations, ranging from additional summits to meetings of the foreign ministers and regular discussions by officials on regional conflicts.

*A cultural exchanges agreement which has been worked out by the two sides is to be signed with fanfare. Such agreements were standard from 1958 to 1979, when the last one was suspended due to the Soviet invasion of Afghanistan.

*A Northern Pacific Air Safety accord, which was still under negotiation by U.S. and Soviet teams in Washington last night, is probable but not certain.

*A U.S.-Soviet commercial air agreement may be concluded in last-minute negotiations in Moscow Monday if the North Pacific Air Safety accord can be concluded first.

*Opening of a U.S. consulate in Kiev and a Soviet consulate in New York may be agreed in principle if a commercial aviation accord can be signed.

*An expanded U.S.-Soviet program of research on nuclear fusion for civil purposes is in an advanced stage of negotiation, with prospects for completion described as good. Pentagon misgivings about the $3.5 billion, 35-year project appear to be outweighed by scientific assessments that the Soviets are ahead of the United States in some aspects of this research.