President Reagan, on the first leg of his long East Asia tour, promised today to extoll the virtues of democracy and said he expects the Tokyo economic summit to "reflect the dynamism of the day."

In brief remarks at Andrews Air Force Base on his departure, Reagan used upbeat rhetoric to describe his mission and did not mention terrorism, the subject that is likely to dominate his talks with allies over the next 11 days.

Reagan is to attend a meeting of Southeast Asian foreign ministers in Bali, Indonesia, before proceeding to the 12th annual summit of industrialized nations in Tokyo.

"This summit comes at an interesting time," Reagan said. "There is no denying that the winds of freedom are blowing, east and west. They are brisk and bracing winds, sweeping out the old and, I believe, ushering in a new era of freedom, an era in which democracy is once again recognized as the new idea . . . . I expect the Tokyo summit to reflect the dynamism of the day."

Except for a private reception, Reagan had no other activities on his schedule here. His trip to East Asia has been structured to give him plenty of rest time on the way to Indonesia.

Presidential spokesman Larry Speakes told reporters on Air Force One that the United States was pleased with British actions against Libyans, including the expulsion of about 300 aviation specialists.

"These are important steps that allied governments are taking. Virtually all the allies have taken some sort of steps. We think the more they take to clamp down on potential terrorists, the better it is," he said.

Asked about Libyans in the United States, he said, "We've got a very limited number, and I don't think we've got any working on our airplanes. There's just 3,000 or so in the United States."

Among those accompanying the president today were Secretary of State George P. Shultz and White House chief of staff Donald T. Regan, national security affairs adviser John M. Poindexter and other top White House aides.