South Korea's two liberal presidential candidates are poised to hold a televised debate late Wednesday as part of their attempt to merge their candidacies before the December presidential election, their aides said.

Moon Jae-in of the center-left main opposition Democratic United Party and independent Ahn Cheol-soo will square off in the 100-minute debate beginning at 11:00 p.m. local time. Three local broadcasters will air the debate.

The two men have been in talks over forming an alliance against Park Geun-hye of the conservative ruling Saenuri Party before Nov. 26, but negotiations got bumpy as they sought to maximize their chances to be on the liberal ticket to the presidential office.

Such tensions prompted Ahn, a 50-year-old political novice, to temporarily suspend negotiations at one point, accusing Moon and his party of being manipulative.

Moon, a 59-year-old former human rights lawyer who served as chief of staff to late President Roh Moo-hyun, has made a series of concessions to meet Ahn's demands including the resignation of party head Lee Hae-chan.

The resignation last week brought the two candidates back to the negotiating table, but talks hit yet another snag over how to conduct opinion polls that would decide which candidate will become the single candidate.

Prospects for an alliance between the two men are seen as a game changer that would determine the fate of the election, as they are seen as liberal alternatives to Park.

The presidential election is slated for Dec. 19, with President Lee Myung-bak constitutionally barred from seeking re-election.