A chastened Nakasone renews his vows

The newly reelected prime minister of Japan, Yasuhiro Nakasone, pledged Tuesday that ''a Japan open to the world'' would maintain and expand international cooperation while ''avoiding trade frictions with other countries.''

He noted that he had retained Foreign Minister Shintaro Abe and Finance Minister Noboru Takeshita to emphasize continuity in international and economic policy and said he was sending Mr. Abe to Washington to exchange views on Japanese-American relations.

On defense, Mr. Nakasone recalled a promise made to President Reagan to increase defense efforts. But the defense budget, he said, would have to be worked out in relationship with the budget as a whole, which is expected to be very tight in order to hold down deficit spending.

Defense spending, Mr. Nakasone said, would remain below 1 percent of gross national product. This does not leave much room for expansion, since this year's

Mr. Nakasone admitted that the issue of political morality had played an important role in the Liberal Democrats' election setback Dec. 18 but denied that the voters' ''no'' extended to his domestic and foreign policies.

On political morality, he said he had asked every Cabinet minister to disclose his assets and that every minister had agreed. He repeatedly denied that former Prime Minister Kakuei Tanaka, whose conviction on bribetaking was the focus of the morality issue, had any direct influence on him or on Cabinet and party decisions. But he admitted he had not done enough to dispel public perceptions regarding Mr. Tanaka's influence.

The new Nakasone Cabinet is Japan's first coalition Cabinet since the Ashida and Katayama Cabinets in 1947 and 1948. The Liberal Democrats were forced into a coalition with the tiny New Liberal Club in order to obtain a stable majority after their election defeat. The leader of the New Liberal Club, Seiichi Tagawa, has become home affairs minister, and the group will also be offered a parliamentary vice-ministership.