A former presidential chief of staff during the Roh Moo-hyun administration indicated Sunday he will announce his presidential bid soon after the main opposition party's convention slated for early next month.
Moon Jae-in, an advisor to the main opposition Democratic United Party, said he "prepared his heart" for the presidential bid but suggested the announcement would be made after June 9 when his party is to hold the convention to select its leader.
He made the comment to reporters ahead of hiking a mountain in the southwestern city of Gwangju in memory of former President Roh, who killed himself in 2009 amid a widening corruption probe involving his family.
Roh made the hiking trip to the Mudeung Mountain in May 2007 after attending a ceremony marking a pro-democracy movement.
Moon was elected as a lawmaker in the country's second largest-city of Busan in April.
Moon said whoever is elected as his party's candidate for the December presidential election, he or she will have to compete with Ahn Cheol-soo, a prominent software entrepreneur, to become a single opposition candidate in an apparent move to boost the opposition's chance of winning the election.
Ahn has yet to clearly announce his presidential bid, though he has maintained generally high ratings in opinion polls. He once led Park Geun-hye, a leading presidential hopeful of the ruling Saenuri Party, in polls.
Ahn, a former medical doctor who gained fame in the 1990s after establishing an anti-virus software firm, is widely popular, especially among young Koreans, due largely to his clean and upright image. He is now dean of the Graduate School of Convergence Science and Technology at Seoul National University.
President Lee Myung-bak's single five-year term ends in February and by law, he cannot seek re-election.