TOKYO, MAY 24 -- Forty-five years after defeat in World War II forced Japan to end its colonization of Korea, the Japanese government explicitly apologized for the first time today for subjugating the Korean people.

Emperor Akihito, welcoming South Korean President Roh Tae Woo to an Imperial Palace banquet on the first day of Roh's three-day visit here, expressed his "deepest regret" for the sufferings Japan caused.

Prime Minister Toshiki Kaifu, meeting with Roh earlier, expressed "sincere remorse and honest apologies for the fact that there was a period in our history in which Japanese actions inflicted unbearable suffering and sorrow on the people of the Korean Peninsula."

Although Japanese leaders had acknowledged "errors" before, none had used the word "apology," government officials said tonight.

Japan's Asian neighbors have often criticized this island nation and compared it unfavorably with Germany for its refusal to admit and apologize for its wartime conquests and atrocities. Although Japan has embraced democracy and renounced aggression since its defeat, these countries have said Japan's unwillingness to apologize indicates that it might once again seek military might to bolster its economic power.

A top government spokesman, Taizo Watanabe, said tonight that the apologies to Roh show that something fundamental has changed.

"I think the people in Japan are free from any possible complex, either superiority or inferiority, toward Koreans," Watanabe said. "So this feeling which may have been strong that we should not apologize is not strong anymore."

Still, many in Japan had opposed any words of apology, particularly from the emperor. Akihito's statement, which acknowledged Japan's wartime responsibility more directly than his father, the late emperor Hirohito, was a product of weeks of internal debate and delicate negotiation with South Korea.

Roh and many of his compatriots had insisted that the two neighboring nations could not move forward in their relationship until the emperor offered a "clear" apology for colonizing Korea from 1905 to 1945 and forcing its people to adopt Japanese names, abandon their language and religion and, in many cases, fight or slave for the Japanese empire. Since the colonization was carried out in the emperor's name, many South Koreans said, only an apology from the emperor could satisfy their national pride.

But many Japanese agreed with the leader of the conservative ruling party who said Japan should not "kowtow" to Korea. Others argued that the emperor, as a powerless symbol, should not be used to state official policy.

In his response to Akihito tonight, Roh did not say directly whether he had heard the apology he had been waiting for. But he did say it was time to "forge a new era of friendship and cooperation . . . putting the mistakes of the past truly behind us."

"It is not possible to erase or forget historical facts," Roh said but then added, "It is significant that Your Majesty, the symbol of Japanese history and the new Japanese nation, has shown deep concern about this matter."

Roh and Akihito in one sense symbolize a new era for the two countries. Roh became South Korea's first freely elected president in 1987 after decades of military rule, and Akihito allowed Japan to truly enter a postwar era when he became emperor on his father's death last year. Both men are old enough to remember the colonial era but too young to bear any responsibility for it.

Yet the painful history of the nations' relationship overshadowed their first meeting today and had threatened to sour Roh's entire trip, the first here by a South Korean leader since President Chun Doo Hwan visited in 1984. When Japan's ruling party said Akihito should say nothing more than his father did during Chun's visit, Roh said the South Korean people never understood whether Hirohito had apologized. Polls showed a majority of South Koreans believed Roh should cancel his trip.

Akihito did repeat his father's words tonight: "It is indeed regrettable that there was an unfortunate past between us for a period in this century, and I believe that it should not be repeated." But then Akihito continued, acknowledging for the first time who was responsible for the "unfortunate past."

"I think of the sufferings your people underwent during this unfortunate period, which was brought about by my country, and cannot but feel the deepest regret," Akihito said.

South Korean officials said after the emperor's speech that they believed it represented a step forward but that not all Koreans would find it satisfactory. Korean reporters, at the urging of South Korean officials, first translated Akihito's last phrase to mean "deep repentance," but then corrected their dispatches, using a Korean word meaning "deep regret" or "lamentation."

In a speech prepared for delivery Friday to the Diet, or parliament, Roh noted that "there still remains a psychological barrier that hinders the evolution of genuine friendship between our two peoples."

"When Japan fully opens up to history and the world, it will be able to present a new image, especially to Asians," Roh said.

Watanabe, the Japanese spokesman, said Kaifu's statement was "more straightforward" and "much stronger" than that of any previous leader. Roh responded that Kaifu had expressed "a correct view of history" and said he "valued the prime minister's statement highly," Watanabe reported after their meeting.

Kaifu also pledged to ease the difficulties of three groups of Koreans who suffered especially from Japan's imperial role: those whom Japan brought to Sakhalin, then part of its empire, to work in coal mines and were then stranded there when that northern peninsula became part of the Soviet Union; those who stayed in Japan after the war and have remained aliens here, unwelcome in Japan but without homes in Korea; and Koreans suffering from radiation sickness because they were in Hiroshima or Nagasaki when the United States dropped atomic bombs.

Kaifu pledged $26.5 million to aid the atomic survivors, now estimated to number as many as 20,000.