SONGNAM, SOUTH KOREA, OCT. 11 -- South Korean opposition leader Kim Dae Jung moved a step closer today to declaring himself a candidate for president, telling an enthusiastic crowd of at least 50,000 followers here that he would "never betray" their wishes.

In a speech that was frequently interrupted by chants of "Run for president," Kim held back from formally announcing his candidacy, but indicated strongly that in the next few days he will decide to throw his hat into the ring. This would widen the split in the opposition to South Korea's government. Kim Young Sam, president of the opposition Reunification Democratic Party, formally declared his candidacy yesterday.

"Many have stressed that if I give up a try at the presidency, it means that I am betraying the people who support me," Kim Dae Jung said. "I will never betray you."

Kim's speech at a park in this town on the outskirts of Seoul was being closely watched for signs of the opposition leader's strategy. While Kim Young Sam's sudden announcement yesterday appeared geared toward pressuring Kim Dae Jung to step aside, the combative speech today appeared to signal a battle between the two leaders that could continue until election day.

Many nonpartisan opposition officials in Seoul worry that the two Kims could split the opposition vote, possibly allowing Roh Tae Woo, the candidate of the ruling Democratic Justice Party, to squeak through with a minority victory. The election, regarded as the first democratic contest in South Korea in several decades, is to be held before Dec. 20.

Kim Dae Jung began his hour-long speech by acknowledging the widespread unease in opposition circles over the breakdown last month in talks between the two Kims to produce one opposition candidate. "I apologize for failing to produce a unified candidate," he said. "It's more agonizing for me than being in prison."

At the same time, Kim said a compromise with Kim Young Sam could be delayed until a few days before the election. "Even though we have not yet achieved a single candidate, we still have two months to work on it," he said. "If in the last days it is necessary, I promise that we will make any sacrifice to prevent a ruling party victory. . . . I promise you that there will eventually be a single candidate to defeat the ruling party."

It is widely believed that Roh would lose if only one of the Kims ran. The National Coalition for a Democratic Constitution, the main nonpartisan opposition group, has warned that the two Kims would be viewed as "sinners before history" if they both ran.