TOKYO, FEB. 8 -- Longtime South Korean opposition leader Kim Young Sam resigned as president of his party today in the most dramatic fallout thus far of the opposition's failure to win the December presidential election.

Kim said he was stepping down to allow the demoralized opposition, still divided between his supporters and those of Kim Dae Jung, to unite before legislative elections now expected next month.

"I feel guilty about the opposition's failure to unite for the coming general election," Kim Young Sam said at a surprise news conference at headquarters of his Reunification Democratic Party in Seoul today. "I feel this is the demand of history."

The two Kims, who have opposed the authoritarian governments in South Korea for the past two decades, were roundly criticized when they both insisted on running in the Dec. 16 election, the first in 16 years.

Together they polled 55 percent of the vote, with Kim Young Sam slightly ahead, but the opposition split helped ruling party candidate Roh Tae Woo win the election with a plurality of 37 percent.

Analysts in Seoul said it is too soon to predict whether Kim's unexpected announcement represents a temporary stepping away from power or a turning point in Korean politics. They said that Kim still may try to control his party, the largest of two main opposition groups, despite his pledge to renounce all leadership roles.

During a recent interview, Kim appeared weary and dispirited. Analysts said he seemed sincere in his decision to step down, stunning even his closest aides. Many other politicians who had predicted the demise of both Kims -- and of their style of politics based on personal loyalty and factionalism -- were surprised only by the timing.

"Even taking a cynic's view that he's not going to retreat, these things once begun are difficult to predict," a western diplomat in Seoul said. "What is implied here is that opposition politics are ready to move on to the next stage, where they're not so leader-oriented."

Kim Dae Jung, who also has faced calls to step down in the wake of what many see as December's squandered opportunity, did not comment today. His aides said he would meet with leaders of his Peace and Democracy Party Tuesday.

"We are definitely hearing that this puts pressures on Kim Dae Jung," the diplomat said.

Kim Young Sam's resignation answers a demand of about a dozen younger politicians in both parties who have been urging both Kims to resign. But it remains unclear whether such junior members will have the strength to assert their leadership.

Kim Young Sam, during the interview in his office, said, "I tried my best to win the election with all the energy and resources that I had." But he said that since the election, "instead of celebrating, Korean people have been spending gloomy days."

Kim said then that he had recovered from his "gloom" and "shock" and he gave no indication that he was considering stepping down. In fact, he repeated his call for Kim Dae Jung -- whom he has not met since the election -- to join his party.

But he also said that a leader must correct his course when he is mistaken, "because no human being is perfect."

Kim was referring to his vow, shortly after the election, to fight for Roh's overthrow, even with his life. Kim backed away from that pledge after a few days and said he would participate in National Assembly elections.

Special correspondent Young Ho Lee contributed to this report from Seoul.