President Bush said farewell to Japan's new emperor Saturday and turned his attention to China, his next Asian stop, saying the "relationship is healthy" between Washington and Beijing.

Bush was making a nostalgic weekend return to his former diplomatic post in China."Both countries have come so far since my stay in China 13 years ago," Bush said in written responses to questions posed by Xinhua, the Chinese news agency. The remarks were released by the White House as Bush prepared to leave for Beijing.

Bush said the world remained "a tumultuous, dangerous place," but said he was optimistic. "I would say that any man with 11 grandchildren is a cautious optimist by definition. He has a big stake in the future."

Although Bush's Asian tour so far has been distracted by the burgeoning battle with Congress over Defense Secretary-designate John Tower, the president earlier sought to stress the primary reason for his visit to Japan - Emperor Hirohito's funeral.

He called it "beautifully staged and beautifully carried out."

Bush met briefly at the Imperial Palace with Japan's new emperor, Akihito, and also planned to meet with Presidents Jose Sarney of Brazil and Ibrahim Babangida of Nigeria, bringing to 20 the number of foreign leaders he has met with in two days of fast-paced diplomacy here.

In his remarks to the Chinese news agency, Bush declared that "the one constant in today's world is change. For the most part, the direction of change is positive from the standpoint of America's values and interests."

"Let me say that I certainly agree that the current state of our relationship is healthy," he said.

"It would be far too optimistic, at this point, where the deterrence provided by U.S. forces in Korea is no longer needed," he said.

Bush and his wife, Barbara, were to board Air Force One later in the day for the nearly five-hour flight to Beijing. In 1974-75, Bush served as the chief U.S. representative in China before the two nations established formal diplomatic ties.

During his two days in Beijing, Bush is slated to hold one-on-one sessions with the nation's top four leaders, discuss matters ranging from Taiwan to trade, and even host a Texas-style barbecue.

Despite the hectic pace, crammed schedule and lack of sleep, Bush said, "I thought I'd be more tired. . . . I feel like a spring colt, ready to charge."

In Bush's meeting with Philippine President Aquino, he vowed continued strong support for a proposed $200 million in aid to the Pacific nation contained in budgets submitted by both himself and former President Reagan, Marlin Fitzwater, his spokesman, said.

The spokesman said Bush talked about East-West relations, trade and NATO in his meeting with West German President Weizsaecker; about residual Cuban influence in Angola in his session with President Mobutu of Zaire.

Bush also met with Singapore Prime Minister Lee Kuan Yew, Belgian King Baudouin, Turkish Prime Minister Turgut Ozal, Pakistani Prime Minister Benazir Bhutto, Italian President Francesco Cossiga.

In addition, the president and his wife had dinner with King Juan Carlos of Spain and his queen, Sophia.

Meanwhile, Baker held a separate session Friday with Japanese Foreign Minister Sousuke Uno that included a discussion of a controversial proposed joint venture to build the FSX jet aircraft.

Although the Reagan administration approved the agreement for Japanese-U.S. construction on a new version of the F-16 fighter, the Bush administration is reassessing the proposal.