Washington — As the superpower summit draws near, the Reagan administration continues to tread a careful course of holding down public expectations -- without sounding unduly pessimistic. A mood blended of uncertainty and hope has emerged here amid conflicting signals of what may or may not be accomplished at the get-together in Geneva. Tonight President Reagan will address the nation in an effort to set the tone for his first meeting with Soviet leader Mikhail Gorbachev and to give Americans a sense of what he expects from the summit.
Striking an upbeat tone, the House Democratic leadership gave strong backing to the President yesterday as he prepared for his departure and pledged a bipartisan willingness to support agreements reached at the summit.
``Geneva is a time for the United States to test the Soviets' sincerity,'' stated House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts. ``If they truly believe that war would only come if we tried to intervene in their country, there is a real hope for peace in the world.''
At the same time Democratic leaders suggested they would like to see two accomplishments at the summit: The first is reaffirmation of the ABM (Anti-Ballistic Missile) Treaty, including a ban on the testing, development, and deployment of the President's Strategic Defense Initiative (SDI), or so-called ``star wars.'' The Soviets have made progress on an arms control agreement contingent on the US's limiting the program.
The second accomplishment Democrats would like to see is an agreement to continue negotiations aimed at a moratorium on the testing and development of antisatellite weapons.
Meanwhile, as the presummit positioning continues on all sides -- at home and abroad -- recent developments point to some hopeful signs as well as some obstacles:
The President has virtually ruled out achieving a major arms control agreement but says he hopes the summit will produce some kind of signal to the arms negotiators in Geneva.
Recently, Mr. Reagan surprised observers by telling Soviet journalists that he would not deploy SDI until both sides did away with their offensive nuclear missiles. He subsequently said this did not mean the Soviets had a veto over his space-based defense plan. This week he further commented that he would make defensive systems available to the Soviets but ``at cost.''
It is not clear whether the summitteers will agree on some ``guidelines' to steer negotiations on an arms agreement, as presidential arms controladviser Paul H. Nitze has indicated might be possible. Some administration officials suggest prospects are better for progress toward an agreement on intermediate-range weapons in Europe than for an accord on strategic (intercontinental) weapons.
Bilateral issues look to be the most promising area of progress. The two sides are trying to work out advance agreements on cultural exchanges, the resumption of commercial air travel between the two countries, and the estabishment of consulates in New York and Kiev. But even these efforts are encountering tough sledding, US officials say.
The President will raise human rights issues in Geneva, citing specific cases of Jews and others refused permission to leave the Soviet Union. But in a departure from his previous stance, Reagan is now stressing ``quiet diplomacy'' as preferable to embarrassing the Soviet leadership in public, a shift that many diplomats had been urging.
In another development, the Defense Department will soon send the President a report on alleged Soviet violations of arms control agreements. The study will catalog Soviet actions that have already been made public. But, in what looks to be a desire not to roil the waters on the eve of the summit, an accompanying report on proposed US responses to the violations will come at a later time.
In an interview with West European journalists this week, the President also indicated the summit meeting might end without a final communiqu'e. ``I'm not a great fan of communiqu'es,'' he told them. ``I think it would make far more sense if each one of us came forth and gave our own view of the meetings and what had been achieved, told frankly what had been accomplished and what hadn't.''
But Reagan told the reporters that he felt the summit would achieve a measure of success if agreement were reached to hold future meetings and continue discussing problems.
It is difficult to know whether the administration's low-key posture is simply presummit positioning to avoid generating hopes that might be dashed, or whether it reflects a genuine assessment of what is realistically possible. But administration officials stress that, even if there is no arms breakthrough at the summit, reaching accords on some lesser issues can be reckoned an achievement, making possible a more stable US-Soviet relationship.
The mood of gloom which set in after Secretary of State George P. Shultz's recent visit to Moscow is viewed as unfounded. ``We know that the Soviets hang tough, nit-pick, and read speeches by Lenin . . . to wear down the other side,'' said one US official. ``When that does not help, you begin to get some movement at the last minute.''
Indications are that some bilateral accords are likely to be firmed up before the summit. As for the key issue of arms control, President Reagan is expected to make up his mind in Geneva based on his discussions with the Kremlin leader.