Meanwhile, acting South Korean President Hwang Kyo-ahn has confirmed that he will not be in the race.
"To stabilise state affairs and fairly administer the presidential election, I've reached the judgement that it is inappropriate for me to run in the election," Hwang was quoted as saying at a Cabinet meeting by Yonhap News Agency.
Hwang had been seen as the best hope of challenging the domination of liberal frontrunner Moon Jae-in based on popularity surveys, as conservative politics has taken a beating over its association with scandal-hit former President Park Geun-hye, reports Anadolu news agency.
The floor leaders of three out of four major South Korean parties also agreed on Wednesday to push for a referendum on constitutional reform on the same day as the election.
One of the key questions being debated is whether to swap the country's single five-year presidential term limit for two four-year terms.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)