The White House held a presummit pep rally this week for its "Star Wars" missile defense program, urging conservative leaders to promote a Strategic Defense Initiative that is "optimistic and imaginative, just like the Republican Party."

The off-the-record briefing, cosponsored by three conservative groups, was one of a series of events to promote the Pentagon's prized research effort before President Reagan travels to Geneva to meet Soviet leader Mikhail Gorbachev. One cosponsor of the meeting, the Coalition for SDI, is also airing television commercials urging support for a "peace shield."

Sven Kraemer, arms control director for the National Security Council, assured the Wednesday briefing that SDI will not be "bargain-chipped" away in Geneva, according to one briefing participant. Kraemer told the group that the "Soviet buildup makes Hitler's buildup look like kindergarten," according to another participant.

Mitchell E. Daniels Jr., top White House political aide, was quoted by a participant as likening the program to the GOP and called it a "marvelous affirmative policy."

"It asserts the fundamental morality of peace through strength," Daniels said, "and the fundamental morality of peace through technology."

The White House Office of Public Liaison, which organized the briefing for about 150 people, declined to discuss it yesterday. Officials there referred inquiries to Steven Trevino, a Defense Intelligence Agency analyst who also chairs the Virginia chapter of Citizens for America.

Trevino said he requested the White House briefing to help "create an environment in which conservative groups will more enthusiastically work together."

"The White House said, 'Great, that's the sort of thing we do anyway,' " he said.

Trevino, a Soviet specialist at the Pentagon, said his work for Citizens for America is unrelated to his official duties. The group was founded by Reagan's "kitchen cabinet," a group of wealthy California businessmen who have supported Reagan for decades.