Soviet foreign policy focuses on test ban. Moscow sees its halt to nuclear weapons tests as a litmus test for the good intentions of the US. But American officials don't think it's that simple.

The Soviet demand for a moratorium on nuclear weapons testing, followed by a treaty banning such tests, has emerged as the centerpiece of Kremlin foreign policy. The nuclear accident at Chernobyl in the Soviet Ukraine probably did not do any permanent harm to East-West relations. But neither did it help to foster them. Nor did it promote solution of the vexing problems still dividing the two sides.

There is still no firm commitment on a US-Soviet summit. [East-bloc sources say summit will take place this fall. Story, Page 11.] The Soviets, although hinting at a desire to withdraw troops from Afghanistan, are bogged down in a guerrilla war that seems to have escalated in recent weeks. And neither the United States nor the Soviet Union report significant progress on the key problem of nuclear arms control.

The US refusal to go along with the Soviet demand for a nuclear test ban, which the Soviets have unilaterally extended to Aug. 6, seems to have further soured relations. Continuing US opposition to a test ban seems to be more of an irritant than other recent developments have been, including the US bombing of Libya, a Soviet ally, or the uproar in the West over Chernobyl.

``My impression is that the Americans are upset about a threefold or fivefold increase in [background] radiation, but they're willing to run the risk of nuclear war,'' said Vladimir Bogachev, a writer for the Soviet news agency Tass, in an interview.

A high-level group of private US citizens heard a similar message from Soviet officials last week during a week-long meeting in Baku, the capital of Soviet Azerbaijan.

According to the Soviet participants, which included a number of senior figures in the Communist Party and Foreign Ministry, the present US administration is by far more intractable than any of its recent predecessors.

``Political will is needed'' to overcome the present stalemate, says Kremlin spokesman Vladimir Lomeiko. ``Washington,'' he says, ``lacks the political will.''

In the Soviet view, an agreement to halt nuclear weapons tests would halt nuclear arms competition between the superpowers and improve prospects for future political relations.

Mr. Lomeiko says a test moratorium would provide a ``firm basis'' for a summit meeting in the US. So far, the Soviet Union has not replied to a US invitation to a summit in June between President Reagan and Soviet leader Mikhail Gorbachev, claiming it must produce ``concrete'' results.

US Assistant Secretary of State Rozanne Ridgway, in congressional testimony this week, said the US expects a reply ``any day,'' but conceded that a summit would be unlikely until after the US elections in November.

Meanwhile, the US set off its fourth nuclear test of the year this week, drawing an angry response from Tass, which branded it ``contrary to the demands of the world public that an end be put to the nuclear arms race.''

``A nuclear test ban,'' says Lomeiko, ``is the most realistic'' approach to nuclear arms control, because it does not require any complex formulas on agreements on the size and capability of the superpowers' nuclear arsenals.

``It could be done tomorrow if we all wanted it,'' he says.

Thus, the Soviet demand for a halt to weapons tests has emerged as a ``litmus test for the good intentions of the other side,'' says Mr. Bogachev.

US officials say they don't believe it is that simple. The US ambassador to the Soviet Union, Arthur Hartman, recently submitted an article elaborating the US view to the Soviet government newspaper Izvestia after the Washington Post published an article by the departing former Soviet ambassador to Washington, Anatoly Dobrynin. Izvestia refused to publish it.

In it, Mr. Hartman argued that: ``Elimination of nuclear weapons is only part of the solution to the problem of maintaining peace. My government would like to make progress across the board to correct conventional and other force imbalances, to ensure compliance with existing and future treaty obligation and to settle regional conflicts.''

Mr. Dobrynin had another article published this week, this time in Czechoslovakia's Communist Party newspaper, Rude Pravo, in which he pointedly referred to one of those regional conflicts.

``In the near future,'' he said, ``the Soviet Union would like to withdraw the Soviet forces that are in Afghanistan. . . . A timetable of their phased withdrawal has already been agreed with the Afghan side,'' he said.

Indeed, US participants at the meeting in Baku reported a similar message from the Soviets. They said ``we want to get out,'' according to Harold Saunders, a former US assistant secretary of state and now a resident fellow at the American Enterprise Institute for Public Policy Research.

The challenge for the US administration, says Mr. Saunders, is to avoid building up fears. But he says the current administration sees US-Soviet relations in terms of a ``business deal'' rather than a ``relationship.''