As Japan backs away from a legislated apology for its aggression in World War II, the Clinton administration has decided to tone down its planned commemoration of the 50th anniversary of the war's end, sparing Japan's prime minister from facing his nation's former adversaries.

Japanese and U.S. officials here say the White House originally proposed a glittering assemblage of heads of state for a memorial ceremony at Pearl Harbor on Sept. 2 - the 50th anniversary of Japan's formal surrender. But that plan reportedly has been redesigned, in part because Prime Minister Tomiichi Murayama objected strongly to it.Current plans call for President Clinton to speak in Honolulu that day. But the other nations that fought in the Pacific theater will be represented by Cabinet-level officials, not heads of state - a low-key format acceptable to the Jap-an-ese.

In another gesture toward Japanese sensitivities, Washington has assured Tokyo that U.S. government representatives at commemorative events will avoid using the traditional term "V-J Day," short for "Victory-over-Japan Day," to describe the end of the Pacific War. Instead, all American material will simply refer to the "end of the war."

In Washington, an administration official cited additional reasons for scaling back the cele-bra-tion. With several com-mem-or-a-tions taking place in Europe and a summit meeting of Pacific nations due in Japan in November, the official said, another gathering of heads of state was considered excessive.

There are several reasons, officials here say, why the Japanese were so reluctant to have their prime minister invited to a gathering of heads of state of the nations Japan fought in World War II.

For one thing, the unassuming, soft-spoken Murayama is said to be highly uncomfortable at international gatherings. As prime minister of the world's second-richest country, he is obliged to attend some, such as the annual summit of the Group of Seven leading industrial nations. But he reportedly wants to keep the number to a minimum.

Moreover, Japan and Russia on paper are still fighting World War II. The two hostile neighbors, the war's only combatants who have not yet signed a peace treaty, are still arguing over disputed territory. Thus the Japanese do not want to sit down with the Russians in a bygones-be-bygones cere-mony.

But the major problem for Japan, U.S. officials say, seems to be that the government here has still not settled on its official position toward the several countries Japan attacked, invaded or colonized.

A long-running domestic debate about Japan's war responsibility is unlikely to be resolved by Sept. 2.

Murayama, 70, head of the left-wing Socialist Party and a critic for decades of Japan's role in World War II, has long favored a formal apology to the East Asian nations that Japan attacked.

Even Murayama has not gone so far, however, as to call for an apology for Japan's air raid on America at Pearl Harbor, the sneak attack that pulled in the United States.

When Murayama became prime minister - through political bargaining - last summer, he extracted a written promise from other members of his governing coalition that the Diet, or parliament, would pass a formal resolution of apology to Asian nations. This was to be done in time for this year's 50th anniversary memorial events.

Various ideas for the resolution, known as the "Remorse, Apology and No-More-War Resolution," have been floating around Tokyo's version of Capitol Hill. The measure is supposed to come up for formal debate this spring.

But the more conservative members of the governing coalition are rapidly backing away from the basic idea of a Japanese apology. As right-wing groups hold rallies and march through the streets denounc-ing the proposed resolution, many politicians seem to favor either a bland one honoring the war dead or nothing.

The three coalition parties have formed a "project team" to work out specific language. But when the team met in late February, there was so much angry debate that not a word was written.