Progressive Moon Jae-in elected president in South Korea, favors dialogue with North Korea

Moon Jae-in favors greater dialogue, negotiation with Pyongyang.

SEOUL, South Korea -- Moon Jae-in, a longtime opposition leader who favors opening a dialogue with North Korea, is claiming victory as South Korea's next president, ending a decade of conservative rule.

So far, 75 percent of the votes have been counted, with Moon garnering 39.8 percent, Hong at 25.7 percent and Ahn at 21.4 percent. Hong and Ahn have already conceded. The official announcement of the winner will be made early Wednesday morning.

He served as a senior secretary to then-President Roh Moo-Hyun from 2005 to 2006, then as his chief of staff from 2007 to 2008.

Moon's administration is expected to take a softer approach in dealing with North Korea, signaling a possibly turbulent ride for U.S.-South Korea relations.

Moon said the previous conservative government's hard-line approach to North Korea failed to prevent Pyongyang from developing nuclear bombs and missile programs. He favors engagement and greater dialogue. He repeatedly pledged during his campaign that South Korea would have an independent voice in the international community.

North Korea has consistently supported Moon's victory, with its state media on Tuesday encouraging South Korean voters to "judge the puppet group of conservatives."

The new administration will likely reopen the Kaesong Industrial Complex, an inter-Korean industrial park in North Korea, which Park shut down last year to increase pressure on Pyongyang.

ABC News' Yoo Hong and Sooji Nam contributed to this report.