MOSCOW -- Soviet party leader Mikhail Gorbachev is capitalizing on his increasing political strength at home and the erosion of confidence in the Reagan administration in Washington to recast Soviet foreign policy along more flexible and conciliatory lines, Soviet officials and senior western diplomats report.

In this view, Gorbachev, who reportedly is personally involved in the details of these policy changes, appears to be looking beyond the tenure in office of the Reagan administation and is seeking to transform the psychology of Soviet-American relations as the next president comes to power.

"We are trying to deprive you of the bogeyman advantage," a Soviet official said to a recent American visitor. "We will deprive Washington of the image of the Red Devils that the Reagan administration built its policies on."

Cautiously, Soviet officials are beginning to admit in such comments to foreign officials and journalists that their leaders made serious miscalculations about the management of Soviet-U.S. relations over the past decade and bear some of the responsibility for the collapse of detente in the second half of the 1970s.

The air of Soviet-American confrontation eventually helped lead to President Reagan's election and an unprecedented peace-time American military buildup that is further straining a stagnating Soviet economy.

Soviet officials who are allowed to have contact with foreigners routinely calculate the effect of their statements for policy purposes, frequently making it difficult to distinguish between what they genuinely believe and what they would like westerners to believe.

But there is a striking concordance between what such officials are saying and how the most experienced western diplomats here portray Gorbachev's objectives and methods.

"Gorbachev has assembled a sophisticated team around him and they know that what drives defense expenditure is fear of the United States," said a senior U.S. diplomat. "They know that they miscalculated the extent of our weakness after Watergate and Vietnam, and provoked with their own actions our resurgence."

"He wants to get the West off his back for 10 to 15 years, and is prepared to adjust policies to get that," said another western envoy.

Gorbachev appears to be determined to avoid repeating the errors his predecessors made in dealing with a weakened U.S. presidency, comments from Soviet specialists on the United States suggest.

Instead of emphasizing Soviet strength and commitments to defending ideological advances abroad, as his predecessors did, he consistently seeks to persuade the United States and its allies that they can afford to cut defense spending and deal with world tension through cooperative efforts with the Soviet Union.

Those themes were present in Soviet propaganda after Watergate and Vietnam, but were overshadowed by determination to build up an overwhelming Soviet nuclear arsenal and to pursue Soviet goals in Third World conflicts unilaterally. Gorbachev is concentrating totally on the message of conciliation.

"Perhaps after the Reagan administration, neither of us will be interested so much in trying to establish hegemony in world affairs as trying to get our houses in order," said a Soviet foreign policy official. "Perhaps we are in a fortunate coincidence of cycles."

One contrast that strikes a visitor returning to Moscow after a two-year absence is the softening of the rhetoric that Soviet officials use to describe their concerns about President Reagan's Strategic Defense Initiative (SDI), the scheme to station ballistic missile interceptor systems in space.

Soviet officials indicate indirectly that they are aware that the Reagan administration has been able to use their sharp attacks on SDI to argue that the space system must represent a major threat if the Soviets responded so vehemently to it.

While still vigorously objecting to SDI in their comments, these officials now do not go out of their way to bring the subject up or to emphasize in bellicose statements the Soviet Union's determination and ability to overcome SDI militarily if necessary.

Shortly after placing three close allies on the ruling 14-member Politburo of the Soviet Communist Party in June and consolidating his grip on power, Gorbachev launched foreign policy initiatives in arms control, improving relations with Asian nations and positioning the Soviet Union to maintain influence with both Iraq and Iran.

In his statements on these subjects, Gorbachev has impressed diplomats here with his personal grasp of detail and his seeming deep involvement in the fashioning of policy documents.

There is mounting evidence that Gorbachev puts more emphasis on working directly with regional experts from the Foreign Ministry and official research organizations than with the full Politburo.

His recent extended interviews on foreign policy with the Italian Communist Party newspaper L'Unita and with Merdeka of Indonesia indicate that Gorbachev will play the primary role in articulating Soviet initiatives.

When The Washington Post recently requested an interview with Foreign Minister Eduard Shevardnadze, one Soviet official pointed out that Shevardnadze has not yet given an interview to the Soviet press and that there are no plans for him to do so.

The suggestion was left implicit that Shevardnadze could not match Gorbachev's mastery of the complex foreign policy network being developed here.