Sen. Richard G. Lugar (R-Ind.), incoming chairman of the Senate Foreign Relations Committee, said yesterday that President Reagan is correct to pursue research into development of defensive weapons in space and should not yield to pressure to treat his "Star Wars" initiative as "a bargaining chip" in arms-control talks with the Soviet Union.

At a breakfast meeting with reporters, Lugar said he agrees with the administration that the defensive initiative could help slow or end the nuclear arms race. He said:

"It is abhorrent that the United States should be vulnerable to a first-strike nuclear attack. The president has asked the right question: Must this be inevitable forever, or shouldn't our best scientists take a look at whether there are ways to change the situation?"

The United States and Soviet Union are scheduled to hold arms talks in Geneva next month, and the Soviets have called for the demilitarization of space as part of these. Lugar noted this yesterday and acknowledged that some U.S. allies -- including British Prime Minister Margaret Thatcher, who is to come here this week -- have expressed uneasiness about the U.S. program.

"At this point, just to see the SDI [Strategic Defense Initiative] as a bargaining chip or something that is dispensable or, worse still, abhorrent is very unfortunate," Lugar said.

He said the uneasiness of Europeans is understandable because their desire for U.S.-Soviet agreements on strategic and medium-range nuclear missiles is so strong that "when new ideas like the SDI come into the conventional order of what they regard as arms-control priorities, it is very irritating to them."

But, Lugar stressed, Thatcher and America's other European allies "have made clear they are not going to disrupt our bargaining position."

Lugar, who has announced plans for hearings early next year on the entire range of U.S. foreign policy, indicated that he is likely to be an administration loyalist with positions slightly to the right of center on most questions. He also made these points on:

* Central America. He said he supports the idea of U.S. aid to the contra insurgents in Nicaragua, not as a means of overthrowing the Sandinista government but to disrupt its ability to supply leftist guerrillas in El Salvador and elsewhere in the region.

But he said fierce opposition to the aid remains in the Democratic-controlled House. He added, "we'll likely end up where we did in the last Congress" when the House blocked further funding of the contras.

* The Middle East. While saying he has "a pretty strong bias toward Israel," Lugar said the United States needs to cultivate close relations with moderate Arab states. He added that it would "not be productive" at this stage for the United States to undertake ambitious new peace initiatives in the region because Israel "has a full plate" dealing with its economic crisis and withdrawal from Lebanon and "there isn't any potential for wider agreements."

* South Africa. Lugar recently joined several fellow Republicans in Congress in urging Reagan to speak out more forcefully against the white-supremacist policies of the South African government. "It is important to make clear that conservatives are not racists, that you have to be consistent in dealing with injustice," he said.