Joint U.S.-NATO research on a "Star Wars" space defense will not necessarily lead to full sharing of all the technological secrets involved, American officials have acknowledged.

This joint research on the Strategic Defense Initiative is a topic on the agenda of this week's summit in Bonn, though no agreements are expected. The weeks leading up to the summit have demonstrated that neither the Americans nor the Europeans are prepared to make the commitments that each apparently wants from the other.

The vision of technological partnership in missile defense, as formally proposed March 26 by Defense Secretary Caspar W. Weinberger, has raised hopes of a new level of cooperation in the North Atlantic Treaty Organization while arousing NATO suspicions of U.S. motives. The invitation to share in the $26 billion program envisioned by the United States has whetted European commercial appetites but also raised strategic and political questions on the continent.

Some Europeans are openly dubious about the value of cooperation, citing past policies of the Reagan administration toward the sharing of secret technologies. For four years the administration has been tightening regulations governing the European nations' ability to obtain militarily useful commercial technology, lest it leak to the Soviet Union.

When West German Chancellor Helmut Kohl said last month that his government plans to join the research phase of the Strategic Defense Initiative, he insisted as a condition that the collaboration "not be a technological one-way street" benefiting only the United States. Kohl, reflecting the concerns of other NATO allies, said West Germany must be granted a "full partnership and guaranteed free exchange" of all findings that derive from the research.

Another German official added, "We want to look inside the black boxes, too."

The administration has not yet indicated that it is prepared to meet Kohl's conditions, relying instead on a vague statement of plans to tap the best brains of the western alliance for a research effort of common strategic importance.

Assistant Defense Secretary Richard N. Perle said decisions to share "Star Wars" research with European participants would be made on a "case-by-case basis." He said, however, that certain technologies are so sensitive that they will have to be "compartmentalized" even within the United States.

Still, Washington intends to treat cooperating allies as full partners, he said in a recent interview, adding that potential technological spinoffs for Europe "are not crumbs."

Another Defense Department official who works in the SDI program said European participants "could be working on a piece of the puzzle without seeing the whole mosaic. There are certain technologies we'll want to keep to ourselves just because of the nature of the beast."

As architect of the administration's hard-line policy on technology transfer, Perle frequently has blamed western allies for leaks of American know-how to the Soviet Union that have compromised U.S. advantages in weapons technology. Now he is assigned the seemingly contradictory role of salesman for allied research cooperation in a venture aimed at producing a new generation of strategic arms.

"It's a wait-and-see thing to see if this guy can really change," said a former senior defense official who works as a private consultant in the international arms trade. "In a way, it's poetic justice."

Perle's conversion is puzzling to industrialists who have fought the administration's curbs on commercial technology transfers and question how it can suddenly speak of sharing the fruits of research on even more sensitive weapons technology.

"I'd be interested in how some of the Defense Department hawks swallow that," said F. Karl Willenbrock, who chairs a technology transfer committee for the Institute of Electrical and Electronic Engineers.

Perle said special arrangements would have to be worked out to protect sensitive information and technology that might flow to European participants. He said U.S. officials would assess the security of any defense firm in deciding to award a contract. Host governments would be expected to provide security assurances for any work at official research centers in their countries, he added.

European diplomats and defense contractors who have had preliminary discussions with Washington express frustration at a lack of clarity and voice wariness of U.S. intentions.

"It's clear that this whole thing hasn't been thought through," said one West German envoy here.

"We have pried out quite a lot about the administration's plans," a British official said. "But little has been offered."

Perle said allied research cooperation could take a variety of forms, including exchanges of scientists and the award of contracts to individual European firms or joint ventures. Among technologies he named as candidates for European research participation are laser projection, kinetic energy, radar, reentry vehicles and data processing.

Perle cited European involvement in the U.S. space shuttle program as an example of "making use of the best talent abroad." The European Space Agency built the shuttle's Spacelab for the National Aeronautics and Space Administration for $1 billion.

The 11 ESA member nations, however, say they have only broken even financially while being denied a fair share of space shuttle time for European astronauts.

Another European concern is whether the administration expects participating countries to help finance the research programs, especially for work performed by government-run laboratories and universities. Although the administration has no announced policy on this, a Pentagon official said, Washington most likely would pay for any foreign research as it does in any contract arrangement.

Staff writer Gary Lee contributed to this report.