When two adversaries possess together more than 17,000 strategic nuclear bombs, it is more reassuring to hear them talking about improving relations than exchanging barbs. The Soviet Union and the United States are visibly toning down the sharp polemics between them and that is worth noting. Soviet leader Yuri Andropov, speaking in the Kremlin with one-time US ambassador to Moscow W. Averell Harriman, says he is ''ready and interested in seeking joint initatives'' with Washington. The United States has responded positively to the Soviet appeal and President Reagan has actually forecast better relations with the Russians - ''because we have a more realistic view of them.''
All this, combined with talk about a possible summit, seems to hold out promise for a better US-Soviet climate. But it is too soon to know what it means in practical terms. There is no doubt Mr. Andropov has immense problems, especially economic ones, and would welcome a decrease in tensions with the United States so that he can get on with solving them. It should also be said that he is shrewdly playing on growing public fears in the West about the nuclear buildup and is seeking to project the image of a peacemaker. This effort has gone so far as to take advantage of a letter from 10-year-old Samantha Smith of Manchester, Maine, asking him why he wanted to conquer the world. Mr. Andropov wrote back that the Soviet Union sought peace with all its neighbors.
President Reagan, for his part, certainly does not wish to let Mr. Andropov run away with the propaganda battle or to be outdone as an advocate of peace and arms control. Under mounting pressure from the nuclear freeze movement at home and in Europe, and under lingering criticism from Congress on his MX plan, Mr. Reagan now appears to be shaping his own image as a peace candidate in the 1984 election. Not irrelevantly, perhaps, the President's chief political adviser speaking before a group of Republican women at the weekend warned of the ''gender gap'' that could endanger Mr. Reagan's reelection. Inasmuch as the peace issue is one on which polls show that a growing number of American women feel strongly, Mr. Reagan is impelled to respond positively to it - and to Mr. Andropov.
The question to be asked is how to translate the latest exchange of more or less kindly words into something concrete. The public should not be fooled into expecting that relations could go back to the ''intimacy'' which Mr. Andropov says prevailed during World War II, when the two nations were allies against a mutual enemy. The public should also not think that it is possible in the near future to have the kind of close, genial state-to-state relationship which exists among the Western allies, bound by common values and systems of government. There will be an adversarial relationship with the Soviet Union as long as its system, its values, and its outlook are inimical to those of the West.
But that should not rule out a normal, even cooperative relationship - one based on a balanced assessment of each other's military strengths, an appreciation of each other's security concerns, and a civil if not friendly posture. In this connection, the appointment of a high-level US diplomat - Jack Matlock, now ambassador to Czechoslovakia - as senior specialist on Soviet affairs in the President's National Security Council is a positive step. This will provide Mr. Reagan with the kind of firsthand experience in and knowledge about the Soviet Union which have been lacking in the White House and should help to bring clarity to American policy on East-West relations.
In sum, the public can be encouraged to see Moscow and Washington stepping back from strident rhetoric, which only aggravates tension. The need, however, will be for the leaders to follow through with progress on the issues which have slipped so noticeably in recent years - trade, cultural exchanges, arms control. Above all, arms control. Mr. Andropov crucially needs the stability which an arms agreement would give him. And President Reagan, now that he has persuaded his country of the need to rebuild its defenses - and to commit more resources to it - is in a favorable position to negotiate with vigor. Will he seize the opportunity?
He will answer the yearnings of millions if he does.