TOKYO (AP) _ Prime Minister Toshiki Kaifu told critics in Parliament today that his summit with President Bush had ''very good results'' in reducing economic friction and was not a case of one-sided yielding to U.S. pressure on trade issues.

''The United States is willing to have a dialogue with us. Do you really believe dialogue is bad?'' Kaifu asked Japan Socialist Party Chairwoman Takako Doi, who delivered a lengthy criticism of his party's policies.

''To avoid going backward, we must continue cooperating,'' Kaifu said. ''I would like to ask for the help and understanding of the whole nation in doing so.''

While ruling Liberal Democratic Party officials saw the summit in Palm Springs, Calif. as contributing to relations with the United States, leaders of the Socialist Party, the largest opposition group, accused Kaifu of weakness.

''What promises did you make to President Bush in the United States?'' Doi asked after charging that Kaifu's trip, on a week's notice, lacked ''adequate preparation or consultations.''

On Sunday, Socialist Party Secretary General Tsuruo Yamaguchi charged that Kaifu had unilaterally yielded to Bush's demands for economic reform in Japan aimed at slimming this nation's $49 billion trade surplus with the United States.

Kaifu denied he had merely yielded to U.S. pressure.

He said a decline in the trade imbalance from a peak of $59.8 billion in 1987 to $49 billion last year was the result of both countries' efforts. He also defended Bush's pledges to cut the $155 billion U.S. federal budget deficit.

''The United States is committed to resolve its problems, and we must also follow through with our reforms and continue our cooperative dialogue with them,'' said Kaifu, who returned late Sunday from the weekend summit.

He faced skepticism, however, over his ability to follow through on promises to Bush that he will reform Japan's distribution system and land use policies, improve living standards and tighten enforcement of anti-monopoly laws.

In talks called the ''Structural Impediments Initiative,'' U.S. officials have said these reforms are needed to eliminate what they call informal trade barriers.

The nation's largest newspaper, the Yomiuri Shimbun, said Bush's requests to Kaifu would ''severely test Kaifu's leadership ability.'' Another major paper, the Asahi, said the challenge would test the entire Japanese leadership.

''The Japan-U.S. Structural Impediments Initiative will end in empty talk unless Japanese companies' overly strong competitiveness and the nature of Japan's closed economy are subjected to close scrutiny,'' the Asahi said in an editorial.

In Palm Springs, Bush also said he wanted to help cut the trade imbalance by reducing the U.S. federal budget deficit, improving education and worker training, increasing savings and investment, and encouraging long-term management strategies aimed at boosting industrial productivity.

Japan is under pressure to show it will implement promised reforms before early April, when trade negotiators are to issue an interim report on the structural trade talks.

Japanese officials expressed concern Kaifu will have problems gathering support for reforms soon enough to satisfy the United States. Kaifu lacks political clout within his own party and faces an upper house of Parliament dominated by the Socialist-led opposition.