Massachusetts Gov. Michael S. Dukakis, in a foreign policy speech here Tuesday, put forth the outlines of a centrist campaign position apparently designed to reassure his establishment audience while leaving room for partisan debate on such issues as strategic weaponry, southern Africa and Central America.

According to his aides, Dukakis' main aim was to persuade the audience of foreign and defense policy experts and U.S. allies that he is "not another George McGovern" promising drastic changes in U.S. foreign policy as did the 1972 Democratic nominee.

Speaking to the annual conference of The Atlantic Council, Dukakis emphasized his strong endorsement of North Atlantic Treaty Organization and approval of President Reagan's current policies toward the Soviet Union.

In doing so, Dukakis gave the administration a green light to try to wrap up a strategic arms treaty and move ahead to begin East-West negotiations on conventional arms reductions in Europe.

Dukakis said his advice to Reagan on a strategic arms treaty is "to go for it."

Reagan, by bringing administration policy on the Soviets close to the traditional Democratic Party position, appears to have put the most potentially powerful and divisive aspects of the foreign policy debate on ice for the 1988 campaign, and as Dukakis' praise of Reagan's performance at the Moscow summit made clear, the president's move toward rapprochement with the Soviet Union has strong bipartisan approval.

Dukakis said he would seek a "steady, step-by-step" policy of improving relations with Soviet leader Mikhail Gorbachev, including regular summits -- just the sort of policy Reagan has dramatically embraced.

In three areas, however, the views Dukakis expressed here Tuesday differed sharply from Reagan administration policy and the basic stance that Vice President Bush, the likely Republican candidate, seems to be ready to run on:

On strategic arms programs, Dukakis repeated his previously stated opposition to placing MX missiles on railroad cars to make them less vulnerable, to the proposed Midgetman mobile missile and the Strategic Defense Initiative, although he cast his opposition this week as a question of budget priorities for the next administration rather than fundamental policy choices.

Dukakis, who is said by those familiar with his views to have an aversion to nuclear weapons similar to that of the two most recent presidents, Jimmy Carter and Reagan, advocated more emphasis on building up conventional military forces, which are usually more expensive than nuclear forces, and went so far as to advocate a U.S. capability for "fighting -- and winning -- a conventional war."

This sounded as if Dukakis would make a major shift in defense policy from new U.S. strategic nuclear programs.

However, Joseph Nye of Harvard University, an adviser to Dukakis who contributed to the Atlantic Council speech, said Dukakis did not mention several strategic programs he favors, among them the highly accurate Trident D5 submarine-launched missile, the Stealth bomber and new cruise missiles, as well as eventual modernization of land-based intercontinental missiles, especially of the single-warhead variety.

As two of his questioners pointed out Tuesday, Dukakis' opposition to the land-mobile MX and Midgetman could have major impact on the strategic arms negotiations.

The formal position of the Reagan administration is to ban land-mobile missiles but in fact it is negotiating with the Soviets toward limitations on such weapons that permit substantial numbers on both sides.

On South Africa, Dukakis took a strong pro-sanctions position that is in tune with Democrats on Capitol Hill and especially with the Jesse L. Jackson campaign but which is at odds with administration policy. Saying that South Africa is engaged in "blatant racism toward its own people . . . in terrorist acts . . . {and} naked military aggression against its neighbors," Dukakis called for a "very tough" policy and declared that the administration policy of "constructive engagement" with South Africa on regional issues has failed.

This stand on the part of the potential Democratic nominee may provide some added impetus to the current drive for new South Africa sanctions on Capitol Hill, and it may add still another complication to the U.S.-sponsored effort to negotiate a regional political settlement in southern Africa before the end of this year.

On Central America and Latin issues generally, Dukakis blasted the administration for "going it alone" with little regard for other nations of the hemisphere.

"Nicaragua's a mess . . . we've fallen on our face again in Panama," charged Dukakis, partly because of a failure to understand the importance of "close collaboration with our democratic neighbors and allies in Central and Latin America."

This sharp criticism was in tune with Democratic Party positions on Central America, which emerged as the most highly partisan foreign policy issue of the Reagan years. And it came as the adminstration was in the midst of an internal debate over whether to ask Congress once more for military aid to the Nicaragua contra rebels.

Dukakis' stand made it clear, if there was any doubt, that such a request would touch off a renewal of a politically charged legislative battle that would bring the contra issue to national prominence once more in a manner that is not likely to be helpful to the candidacy of Bush.