A top defense official said yesterday that the United States should not trade its "Star Wars" research program for reductions in Soviet nuclear missiles, a potential approach to arms control that other administration officials have suggested.

Those officials have said that the United States may win concessions from the Soviet Union by agreeing to restrict the U.S. effort to develop defenses against missiles, which reportedly concerns the Soviet Union.

Whether any portion of the missile-defense program should be negotiable is expected to be an issue in a second Reagan administration if the president is reelected.

Fred C. Ikle, undersecretary of defense for policy, said yesterday that the president's "vision" of a world in which defensive systems negate some of the terror of nuclear weapons should be pursued. He said that the United States gave up its defensive weapons in the early 1970s under the antiballistic missile system treaty but that the Soviet Union did not limit its offensive arsenal as U.S. negotiators had hoped.

"It was a nice theory, but it was disproven by the events of the last 15 years," Ikle said. "Unless something changes, you wouldn't want to go back just like that to a disproven theory."

Ikle also said the administration might opt to build an "interim" defensive system that would protect U.S. nuclear missiles but not cities. It is "possible" that "the initial capability will help protect the deterrent forces," Ikle said.

Critics have said that this approach is contrary to Reagan's call for a system to protect populations and make "nuclear weapons obsolete."

Air Force Lt. Gen. James A. Abrahamson, director of the Strategic Defense Initiative program, said developing a capability to destroy Soviet missiles in their so-called boost phase, within minutes of their launching, was key to any successful defensive system. Nonetheless, he supported Ikle's view that a decision to go ahead with an interim system defending U.S. missiles could be made.

Ikle and Abrahamson spoke to reporters in response to the release of a report from the Council on Economic Priorities that said the administration's Star Wars program was too expensive and unlikely to succeed. The council said that spending $26 billion in the next five years, as the administration intends, was not justified by the maturity of the technology needed to build a missile defense system.

The council also said that spending so much so soon -- as much as the cost of research and production of 100 B1 bombers -- would distort the whole pattern of scientific research in the country. Star Wars will take one-third of all new research dollars in 1986, for example, and much of that will go into research with little applicability to anything but missile defense, the council report said.

Knowledgeable sources said yesterday that Abrahamson's office will seek $3.8 billion in next year's budget, compared with the $1.6 billion Congress allowed for the current year.

Abrahamson disagreed with the council's report, saying his research program was proceeding at a modest pace based on the potential of various technologies. He said that even before Reagan's call to find a missile defense, the Pentagon was planning to spend $15 billion or $16 billion on related research projects during the next five years.

Abrahamson also said his program was trying to "design the research within" the 1972 ABM treaty. Some types of testing would violate that treaty, and critics have said that the Star Wars program is threatening one of the few successful U.S.-Soviet arms-control efforts.