A feisty Japanese legislator named Michio Watanabe said last August that he saw nothing in the United States that anyone in Japan would want to buy.

That remark, made in Tokyo to U.S. Trade Representative Clayton Yeutter, has come to haunt Watanabe, who last month was named Japan's minister of international trade and industries -- the man charged with implementing Prime Minister Yasohiro Nakasone's policy of opening the Japanese markets to imports.

Yeutter, President Reagan's point man on trade, made sure Watanabe knew his comment was remembered.

Since a major goal of the Reagan administration is to get the Japanese to buy more American products to ease record U.S. trade deficits, Yeutter said he plans to change Watanabe's mind.

Watanabe said this week he would have been more diplomatic if he had known he would get his present cabinet post.

The latest Yeutter-Watanabe exchange took place here as trade ministers from the United States, Japan, Canada and the European Community met today to discuss major issues confronting the world trading system.

All this was done with smiles, but it illustrates the underlying differences and the seriousness of the trade frictions between the United States and Japan, its major Pacific ally.

This is the ninth of the so-called "quadrilateral" meetings, which were designed to get the trade ministers in a pleasant, isolated setting to discuss broad issues, instead of specific disputes. The meetings will run until Sunday.

These ministers represent the giants of the world trading system, and, despite their differences, they all espouse a commitment to free and open trade.

Yeutter, host at the third meeting in the United States since the sessions opened in 1982, said this meeting places the "heaviest load" of substantive issues on the ministers.

The opening meeting focused on ways to prevent piracy of copyrights, and patents and preparations for a new global round of trade talks, due to start in September. Negotiations to strengthen and expand the powers of the General Agreement on Tariffs and Trade (GATT), the 90-nation Geneva-based organization that regulates world trade, is a major objective of the Reagan administration. The planning meetings for a new GATT round start in Geneva in 10 days.

While GATT members agreed in November to go ahead with preparations for a new round, the major trading powers still must persuade a group of Third World nations, headed by Brazil and India, to take part.

In two sessions Saturday, the ministers will take up four other major trade issue: strengthening GATT's ability to settle disputes between trading nations; breaking down barriers to international investments; setting up equal pricing for foreign and domestic buyers of natural resources; and designing ways to help failing domestic industries without being protectionist.

Besides the general meetings of the four ministers and their top aides, the "quad" gives the participants a chance to deal with disputes.

Yeutter met with Watanabe Thursday to discuss specific U.S.-Japanese trade frictions. U.S. officials said Watanabe, a former finance minister, expressed great interest in changes in the American economy, especially the chance that the Gramm-Rudman-Hollings law might successfully lower the budget deficit.

He reportedly told Yeutter that Japan is undecided on whether to continue its self-imposed quotas on the sale of cars to the United States after the current restraints end March 31. Yeutter warned the Japanese minister that continued auto restraints or not, Japan faces an antagonistic Congress because of its burgeoning trade surplus, believed to have approached $50 billion with the United States alone last year.