Democratic United Party presidential candidate Moon Jae-in has asked independent hopeful Ahn Cheol-soo for talks on fielding a single opposition candidate in the December election.
Moon said on Tuesday that it is about time to talk openly about the question.
But Ahn was noncommittal, saying that while he does not intend to disagree with Moon they may need some time more before they can discuss the matter.
The opposition camps worry that Moon and Ahn could split the progressive vote, allowing Saenuri Party candidate Park Geun-hye to become president by default.
Speaking before a panel discussion on political reforms, Moon said, "The time has come to discuss when to field a single candidate and when to start that process." Moon added he is willing to hold a one-on-one TV debate with Ahn.
Woo Sang-ho, a spokesman for Moon's election camp, said, "Detailed negotiations must start next week at the latest if we are to decide on a single opposition candidate before candidate registration starts" on Nov. 25-26. He added, "I formally ask Ahn's camp how long they intend to put it off."
Ahn was quoted by his spokesman Yoo Min-young as saying, "I promised to announce my policy plans by Nov. 10, so I have to devote myself to that pledge first." Ahn added it is more important at this point to exchange ideas on the best policies to lead the country.
The head of Ahn's election camp, Kim Sung-shik, said it remains to be seen whether a decision can be made before candidate registration.
If discussions start after Nov. 10, pundits say the only option to pick a single candidate would be opinion polls since there will not be enough time to ask voters directly.