Superpower relations - forward steps for three years. There's been measurable progress across the board

Perestroika - that Gorbachevian goal of restructuring Soviet society - is also rebuilding superpower relations. Less than three years ago, US-Soviet relations were still coming out of a deep freeze and prospects for a thaw seemed limited.

Today, as the Reagan administration accelerates planning for the coming Moscow summit meeting, the change of mood is startling. From progress on nuclear arms control to a marked jump in Jewish emigration from the Soviet Union, the relationship is steadily improving, according to US policymakers.

``Over the past three years we have established a broad, active, and quietly developing relationship, almost from a cold start in '85,'' says a key administration official.

The Moscow summit, expected to be held in late May, will again touch on the four-part agenda that President Reagan has pursued in US-Soviet relations since a major policy speech at the United Nations in the fall of 1985: arms reduction, regional issues, human rights, and bilateral relations. Across the board, there will be measurable progress to record in Moscow:

Arms control. Negotiations on a strategic nuclear arms agreement (START) as well as on nuclear testing and conventional arms talks are proceeding with determination on both sides. Whether the two sides can achieve a START agreement in time for the summit meeting is problematic, but US officials report progress so far.

Regional issues. The most conspicuous change is the Soviet Union's determination to withdraw its forces from Afghanistan. Negotiations for a withdrawal timetable have yet to be completed, but US officials are persuaded the Soviets intend to pull out whatever the result of the talks.

``There's been a revolution in Soviet thinking in the past 14 months,'' a US official says. ``They have decided they have to minimize their liabilities abroad.''

It is likely, officials say, that Soviet withdrawals will be under way when President Reagan and Soviet leader Mikhail Gorbachev meet in Moscow and that, while a joint statement on the issue might be too ``painful'' for the Soviets, some reference may be made to the Soviet intention to pull out all forces by the end of the year.

In Angola, say US officials, there are indications that Moscow urged Cuba to ``be more flexible'' in negotiations over a time frame for withdrawing Cuban forces. Cuba has now agreed, in principle, to a total pullout.

Administration officials also see the Soviet hand in pressing Sandinista leader Daniel Ortega Saavedra to talk directly with the contra rebels in Nicaragua, something the US urged the Soviets to do in the recent ministerial talks in Moscow. The Soviet Union is also encouraging a resolution of the war in Cambodia and a withdrawal of Vietnamese forces. In the Middle East, the Soviets have adopted a moderate course, including holding their fire on US efforts to revive a peace process. ``We sense a willingness on their part to try to be constructive,'' a US official says.

Human rights. Emigration of Soviet Jews could reach 1,000 a month for the first time in many years, administration officials say. The Soviets have given assurances they will not apply restrictive provisions of their law regarding the emigration of immediate family members only. This has been a concern to the American Jewish community. Emigration of Armenians may reach 9,000 or more in 1988, a record high; emigration of Germans will also continue to be high, with between 10,000 and 14,000 expected to leave the Soviet Union this year.

Reagan administration officials stress that much more remains to be done to fulfill obligations under the Helsinki accords of 1975, especially in regard to freeing Soviet political and religious prisoners. But officials are encouraged that discussions of these problems have intensified in a number of forums, including ministerial meetings, and that the discussions are scrutinizing Soviet laws with a view to holding them up to international standards. ``The results fall short, but we're playing in a field we have defined,'' says an official.

Bilateral relations. The broad framework of cooperation set up during the Nixon years has been revived.

Experts from the two sides now meet regularly to discuss projects in such areas as health and health care, space research, nuclear energy, the environment, and housing. Negotiations are under way for cooperation in basic science. Cultural exchanges are back to the levels of the 1970s.

American officials stress that the US has become more hard-headed in vetoing agreements and projects that do not allow for reciprocity or that would impair US interests by the transfer of military and other technology.

While these gains do not spell the end of the adversarial nature of US-Soviet relations or eliminate the potential for recurring tensions and problems, US officials stress, the Reagan administration can take pride in putting ties on a more constructive, business-like path.

It is also acknowledged that the new US-Soviet rapprochement is made possible because Mr. Gorbachev and his Politburo colleagues, driven by an internal agenda, are scaling back Soviet commitments abroad and opting for greater cooperation with Washington.

Second of two articles on US-Soviet relations.