A high-ranking administration official hinted yesterday that the United States might be willing to swap President Reagan's "Star Wars" antimissile defense plan for significant reductions in Soviet offensive nuclear weapons.

"The research program and our intentions for it have to be on the table and a matter for discussion and agreement and negotiation between us," said a senior administration official who briefed reporters on preparations for U.S.-Soviet arms control talks. "And they surely will be . . . . "

The official, who spoke on condition that he not be identified, said that the administration expects the meeting between Secretary of State George P. Shultz and Soviet Foreign Minister Andrei A. Gromyko in Geneva on Jan. 7 and 8 to lead to further negotiations on intercontinental and medium-range nuclear missiles, and on offensive and defensive space weapons.

"We hope to come away with an agreed plan for formal negotiations and dialogue in each of these areas," the official said.

Yesterday's briefing at the White House was the latest attempt by administration officials to perform a balancing act on Reagan's Strategic Defense Initiative (SDI), which he described in an Election Day interview with The Washington Post as "the greatest inducement to arms reduction."

Administration officials proclaim utmost seriousness in exploring a mutual strategic missile defense with the Soviets, saying that a defensive system would be preferable to the current "balance of terror" between the superpowers.

In almost the same breath, however, officials have been suggesting that the United States could trade away its interest in a defensive system if the Soviets are serious about limiting offensive weapons.

On Wednesday, Defense Secretary Caspar W. Weinberger defended the idea of strategic defense, saying that reliance on deterrence "condemns us to a future in which our safety is based only on the threat of avenging aggression."

But when Weinberger was asked after this speech to the foreign press center whether he was excluding the defensive system from negotiation, he replied: "I don't exclude anything . . . . The president has specifically not excluded anything."

Yesterday, the administration official who briefed reporters took issue with formerly prominent U.S. officials who have called upon Reagan to abandon the SDI as incompatible with an arms control agreement. These officials have contended that it is impossible to devise a leak-proof antimissile system.

The administration official said this view is "terribly simplistic and wrongheaded" because a defensive system doesn't have to be 100 percent effective. He said that if the Soviets faced a situation in which 60 percent of their missiles could not get through and they were confronted by "a very substantial response," this would "dramatically affect the Soviet calculus to attack in the first place."

The official was responding to criticisms of the Star Wars proposal made by Robert S. McNamara and McGeorge Bundy, defense secretary and national security affairs adviser in the administrations of Presidents John F. Kennedy and Lyndon B. Johnson. Along with Gerard Smith, arms control negotiator in the Nixon administration, and George F. Kennan, former ambassador to the Soviet Union, they coauthored a recent article in Foreign Affairs quarterly that was sharply critical of the SDI.