TOKYO -- With leaders of government and industry here already fretful about next year's 50th anniversary of Japan's attack on Pearl Harbor, an old controversy has been reignited by the emergence of new documents concerning the late emperor Hirohito's role in World War II.

Since this country is across the international date line from the United States, the Japanese consider Dec. 8 to be Pearl Harbor Day. Other than a few editorials in the papers and World War II movies on TV, the 49th anniversary of the raid was marked quietly here this year. But there is great concern here that next year's Pearl Harbor Day will not be so quiet in the United States.

The fear is that the 50th anniversary of the surprise attack that crippled the U.S. Pacific Fleet -- and eventually sank Japan's Asian-Pacific empire -- will be widely marked in the United States, leading to increased hostility toward Japan.

"Everybody is aware that next year is the 50th, and that could become something important in the United States," said Yuki Okamoto, a senior diplomat in the Foreign Ministry. "There are a lot of ideas around about what Japan might do."

Industrial groups are planning meetings to discuss a possible backlash against Japanese products. A citizens' group is pushing for a formal apology from the Japanese government to the American people. It has been suggested that Japan's prime minister travel to the Pearl Harbor Memorial next Dec. 7 to lay a wreath.

"We've been approached by a lot of nonprofit groups in the U.S. about putting on programs and such," Okamoto said. "We haven't figured out yet how much of this is the private sector's thing to do and how much is up to the government."

Japan is currently engaged in renewed discussion of one of the enduring controversies of 20th-century history: to what extent Hirohito was responsible for Japan's entry into World War II.

The emperor's role in Japan's byzantine internal politics in the 1930s -- particularly the question of whether he pushed or resisted the movement toward war -- is a hardy perennial in the world of academic conferences and doctoral dissertations. But in the past month it has become the stuff of daily conversation here.

The triggering event was the release in the journal Bungei Shunju of a newly found memoir said to relate Hirohito's conversations with his close aides in the years after Japan's defeat.

The document, written in longhand by the late Japanese diplomat Hidenari Terasaki, was discovered earlier this year in a trunk in Casper, Wyo. Terasaki's daughter, Mariko Terasaki Miller, who lives in Casper, was digging through old family papers when she found about 100 pages of notes in her father's handwriting.

Terasaki's notes are said to be verbatim transcripts of monologues in which Hirohito told his aides about events before and during the war. In the notes, the emperor said he did not have the power to stop the military clique pushing for war from going ahead with the Pearl Harbor raid.

"If at that time," Hirohito is reported as saying, "when we had such a strong, well-trained army and navy, I had blocked the pro-war side . . . public opinion would definitely have boiled over. There could have been a coup d'etat.

"If I had vetoed the start of the war, there would have been chaos and civil war. All those around me would have been killed, and my life would have been endangered. If that had to happen, fine -- but then a very barbarous war would have occurred, and Japan might have perished."

Hirohito is reported to have said that Japan's 1889 constitution limited his power when the head of the government, Gen. Hideki Tojo, wanted to go to war. It declared the emperor "sacred and inviolable" as head of state. In fact, like countless Japanese emperors before him who cowered before the shogun, or military chief, Hirohito was constantly used by civilian and military leaders for their own advantage. The memoir shows Hirohito suggesting that he could not stop the military officers who were supposedly acting in his name as they moved toward war.

Historians on both sides of the Pacific have debated Hirohito's role. The majority view seems to be he did not have the legal power or political clout to stop the military leaders from attacking Pearl Harbor. But some historians have argued he was an advocate of the war and an important player in the decisions that led to the attack.