The Japanese yen soared to another post-World War II high against the dollar yesterday, prompting reports that Prime Minister Yasuhiro Nakasone will ask his major trading partners at next month's Economic Summit to join in an effort to keep the Japanese currency from rising any further.

But there were no indications that the United States or the other major industrial nations believe that the yen has appreciated enough, or that the dollar has fallen enough, to help reduce the huge Japanese trade surplus. Treasury Secretary James A. Baker III said in a recent interview that while he was suspending efforts to "jawbone" the dollar down, he had no target in mind for the dollar/yen relationship.

The dollar yesterday fell to 169.35 yen in Tokyo, down from 171.90 on Monday. Reportedly, the Bank of Japan did not intervene heavily to brake the decline, as it did Monday by buying large amounts of dollars. In New York, the dollar dropped to 168.80 yen from 171.15 Monday.

Some market analysts said that part of the dollar's weakness could be attributed to concerns about the strength of the U.S. economy, which had led the Federal Reserve Board to lower the discount rate on Monday.

In Tokyo, there were widely publicized expressions of concern about the extent and rapidity of the yen appreciation, not only from the prime minister but also from his two key financial officers, Finance Minister Noburo Takeshita and Central Bank Governor Satoshi Sumita. They said that the 29 percent rise in the value of the yen since last September had been too much.

At a Sept. 22 meeting, the Group of Five major nations -- Japan, the United States, West Germany, France and Britain -- agreed on a concerted intervention to boost the nondollar currencies, a decision that was carried out with great success. Since the February 1985 peak of the dollar at 262.5 yen, the yen has appreciated 35.5 percent.

Nonetheless, one U.S. analyst, C. Fred Bergsten of the Institute for International Economics here, suggested that "the Japanese are crying a lot of crocodile tears."