A senior member of the Soviet Politburo, Vladimir V. Shcherbitsky, told President Reagan yesterday that Moscow will respond with "both offensive and defensive" military measures if the United States goes ahead with its "Star Wars" space-based strategic defense plan.

Reagan, in what the White House described as "a lively give-and-take," responded that if research proves the Strategic Defense Initiative (SDI) valid, the United States will discuss with the Soviet government "ways to deploy it in a stabilizing manner."

In what may be a preview of arms limitation talks to begin in Geneva on Tuesday, the president urged his Soviet visitor to agree to cuts in Moscow's powerful and "destabilizing" land-based nuclear missiles, according to the White House account.

Shcherbitsky said he responded by urging Reagan to junk the MX intercontinental ballistic missile, calling it expensive and unnecessary.

There was every sign after the 48-minute meeting that the two nations will enter the new arms negotiations deeply divided on the central issues.

Aside from Foreign Minister Andrei A. Gromyko, Shcherbitsky is the first full member of the ruling Soviet Communist Party Politburo to visit the United States since the heyday of Soviet-American detente in 1973. His presence in Washington as head of a delegation of Soviet parliamentarians visiting Congress provided an unusual chance for a high-level preview of arms control positions.

The Soviet Politburo formally adopted instructions for its arms negotiators in Moscow yesterday. Reagan scheduled a meeting with the U.S. negotiating team today to impart his final decisions on the stands they are to take in Geneva.

Reagan's national security affairs adviser, Robert C. McFarlane, one of the architects of the U.S. positions, in a speech yesterday, blamed the Soviets for thwarting previous arms control efforts and agreements.

"History may lead some to doubt that we will make headway" in Geneva, he told Overseas Writers, a journalists' club. "We're not captive by history. We're just trying to make a little."

Shcherbitsky, in a lengthy statement on U.S.-Soviet relations and the arms talks made public by the Soviet news agency Tass, said the mere preparations for the Reagan Star Wars plan, as the SDI is known, would bring about "an undermining of the whole process of arms limitation and reduction."

Implementation of the plan, Shcherbitsky said, "would nullify all the positive things achieved in the '70s," especially the 1972 Antiballistic Missile (ABM) Treaty.

"Neither side can or should strive to achieve military superiority no matter what name it is given, an antimissile or strictly defensive 'shield' or anything else," Shcherbitsky said. "Such an aspiration is simply chasing illusions" and "is extremely dangerous because it leads to a stepping up of the arms race and destabilization of the entire international situation," he said.

Speaking to reporters outside the White House after his meeting with Reagan, the Soviet official also spoke of the possibility of compromises between the two nuclear superpowers. All previous U.S.-Soviet agreements included such compromises, he said, "and if the United States government would go along that line, then a compromise decision could be achieved and people could breathe freely."

Reagan, according to White House spokesman Larry Speakes, told his visitor that none of the U.S. military programs is "meant to be threatening." Speaking of reductions and eventual elimination of nuclear arms as U.S. objectives, Reagan was quoted as saying, "if we can't get reductions we will have to continue modernization of our defense programs."

"We're not going to allow ourselves to drift into inferiority" in the weapons field, Reagan added.

About half the Reagan-Shcherbitsky meeting was devoted to the Strategic Defense Initiative. The United States plans to promote the program at Geneva. Retarding Star Wars is the highest priority Soviet negotiating goal.

Reagan described the SDI as "a research program consistent with the ABM treaty," according to the White House spokesman. Reagan was quoted as telling Shcherbitsky that if the research is successful, "We would sit down to discuss ways to deploy it in a stabilizing manner" with the Soviet Union.

Reagan and other U.S. officials have said at various times that the United States would "discuss" and sometimes that it would "negotiate" with the Soviets before deployment of a space-based antimissile system, which is prohibited by the ABM treaty. But Reagan and others also have said the deployment phase will be up to a future president, since the research phase is expected to continue through the rest of Reagan's second term.

The missile defense plan, Reagan was quoted as telling Shcherbitsky, also could be helpful in dealing with "the madmen of the future," a reference to terroristic governments and subnational groups.

"People don't start wars, governments do," Reagan told Shcherbitsky according to the White House account. He reportedly added that "unfortunately people in the Soviet Union don't have much to say about what their government does." No reaction from Shcherbitsky was reported by Speakes.

Reagan and his Soviet visitor chatted amiably for photographers before their Oval Office meeting.

They were joined by Secretary of State George P. Shultz, White House chief of staff Donald T. Regan and McFarlane, on the U.S. side, and Ambassador Anatoliy F. Dobrynin, Central Committee propaganda chief Boris Stukalin and Foreign Ministry official Aleksandr Bessmertynkh on the Soviet side.

While photographers were in the room, Shcherbitsky said his mood on the eve of the arms talks was merely "so-so."

Reagan also was guarded in his expectations. While saying the Geneva talks are a "forward step," Reagan also said, "It is a very complicated process. It's not just an easy thing to sit down and decide."