China's decision to release dissident Fang Lizhi and his wife Li Shuxian was motivated partly by a desire to win most favored nation trading status from the U.S. Congress and to persuade Western democracies to lift economic sanctions against Beijing, administration officials said yesterday.

Officials said President Bush will probably agree to put the issue of lifting sanctions on the agenda for the economic summit in Houston next month, where leaders of the seven major industrial democracies will also debate aid to the Soviet Union. Japan is expected to take the lead in pressing for renewed investment in China.

Fang's release, in which U.S. Ambassador James Lilly served as an intermediary, was hailed by the White House and congressional Democrats, but they also criticized Beijing for continued repression of human rights.

White House press secretary Marlin Fitzwater said, "This humanitarian action is a farsighted, significant step that will improve the atmosphere for progress in our bilateral relations." Fitzwater said this statement was made available to China in advance.

Senate Majority Leader George J. Mitchell (D-Maine) applauded Fang's release but said he remains concerned "about the lack of freedom available to millions of his fellow citizens." Mitchell said he would continue trying to block most favored nation status for China.

After a year as a virtual hostage in the U.S. Embassy in Beijing, Fang left for Britain aboard a U.S. Air Force C-135 transport after issuing a three-paragraph statement in which he declared his opposition to China's constitution, but promised to "refuse to participate" in anti-China activities. The official Chinese news agency said Fang had shown "signs of repentance," but Fitzwater said the dissident's statement "paralleled many of his public statements in the past."

Fitzwater and State Department spokesman Margaret Tutwiler said the United States made no deals for Fang's release and there was no quid-pro-quo. Lilly helped with the logistics of Fang's departure, they said.

In his statement, Fang said he was leaving China "in order to visit relatives and friends abroad and to obtain necessary medical treatment." Officials declined to provide details about his medical condition, but said concerns about his health were a factor in persuading China to let him leave.

Fang has a son studying in the United States and another in China. Tutwiler said the latter son has applied for permission to study in the United States and "we have no reason to believe" he would have trouble leaving China.

Lilly had repeatedly raised Fang's case with Chinese officials. Former president Richard M. Nixon did the same during a private visit there, telling China's leaders that it was a continuing obstacle to better relations, according to government officials familiar with the visit.

An administration official said several factors led to China's decision. One, he said, was that Fang's outspoken criticism -- which he had made before the Tiananmen Square crackdown on pro-democracy demonstrators in June 1989 -- had stung the leadership. In this view, China also was anxious to remove Fang's case as an irritant in relations with the West.

Another factor, the official said, was Bush's recommendation for renewal of most favored nation status, now before Congress. China has put great stock in retaining the status, which allows Chinese exports to receive non-discriminatory tariff treatment.

Sen. Claiborne Pell (D-R.I.), chairman of the Senate Foreign Relations Committee, said, China's decision "is a clear indication that congressional criticism of China's policies is working."