The issue of China, which views Taiwan as its territory, looms over the Jan. 13 parliamentary and presidential elections.
China has stepped up military and political pressure, including high-profile war games, to press the island to accept its sovereignty claim, which Taiwan rejects.
But both parties failed to reach agreement on how to interpret opinion polls and thus decide who will stand for what position by an originally scheduled deadline of Saturday.
China detests frontrunner Lai, regarding him as a separatist, and has rebuffed repeated calls from him for talks.
Hou especially has vowed to renew dialogue with Beijing, and says Lai is a dangerous supporter of Taiwan independence.
Persons:
Democratic Progressive Party's, Lai Ching, Hou Yu, Ko, Lai, Hou, Hsiao, Eric Chu, Tsai Ing, Ben Blanchard, William Mallard, Kim Coghill
Organizations:
Kuomintang, KMT, Taiwan People's Party, Democratic Progressive, ih, Former Taipei, DPP, Thomson
Locations:
TAIPEI, China, Taiwan, Beijing, United States, Chiayi