The two main opposition groups on the island were fighting over how to decide who will run for president, and with time running out, their possible united effort for the presidency of Taiwan was in chaos on Saturday.

A shadow of China, which sees Taiwan as its territory, hangs over the parliamentary and presidential elections scheduled for January 13. China has increased political and military pressure on Taiwan, including holding public war drills, in an attempt to get the island to recognize its claim to sovereignty, which Taiwan denies.

After weeks of sometimes acrimonious talks on joining up for the presidential election, the Kuomintang (KMT) and the much smaller Taiwan People’s Party (TPP) agreed on Wednesday to look at an aggregate of opinion polls to decide which party’s candidate would run as president and which as vice president.

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. Candidates have to register with the election commission by Friday.

The ruling Democratic Progressive Party’s (DPP) candidate, Vice President Lai Ching-te, has for months led most opinion polls to be Taiwan’s next president, leaving the KMT’s Hou Yu-ih and the TPP’s Ko Wen-je to battle it out for second place.

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.

Some opinion polls have shown that if Hou and Ko teamed up, in whatever combination, they would beat Lai and his presumptive running mate, Hsiao Bi-khim, Taiwan’s envoy to the United States.

Former Taipei mayor Ko, who has previously said the things he hates most are “mosquitoes, cockroaches and the KMT”, asked by reporters whether talks had now broken down said anything was possible before Friday but he could not be expected to “surrender” to the KMT on the poll issue.

“We hope we can continue to consult with the KMT,” he said.

Both parties insist their reading of the polls is the correct one, with the KMT’s showing that if Hou was the presidential candidate then the joint team with Ko as running mate would beat Lai, which is not what the TPP’s shows.

KMT Chairman Eric Chu, speaking at a separate news conference, said cooperation remained the aim, but did not indicate he would back down on the polls issue.

“We hope to reach consensus as soon as possible,” he said.

The DPP, which will on Monday announce Hsiao as Lai’s running mate and champions Taiwan’s separate identity from China, says only China stands to gain from the opposition getting together.

Speaking at a Lai campaign event in the southern city of Chiayi on Saturday, President Tsai Ing-wen said the opposition sought merely to split the spoils of power and them teaming up augured chaos.

“If the two political parties do not have a common philosophy, the operation of the government will suffer from internal friction and will not be able to gain international trust,” she said.

News of the KMT and TPP’s progress on a joint presidential bid this week pushed the Taiwan dollar to its strongest weekly rally in a year on expectations of an easing of Taiwan-China tensions if they won.