Terry Gou, the billionaire founder of iPhone assembler Foxconn Technology Group, threatened to throw Taiwan's presidential race into turmoil as he took a key step toward running as an independent.

Gou withdrew Thursday from the opposition Kuomintang, a necessary precursor to mounting a third-party challenge against President Tsai Ing-wen. The move came despite a last-minute plea from senior KMT leaders including Tsai's predecessor, Ma Ying-jeou, for Gou to back their nominee and help return the China-friendly party to power. Gou has until Tuesday to apply to run in the Jan. 11 election.

"I know I'm doing the right thing, something major that will turn around Taiwan's destiny," Gou said in a statement.

Gou's candidacy would shake-up Taiwan's political landscape, undercut KMT challenger Han Kuo-yu's effort to unseat Tsai and potentially weaken both dominant parties. A three-way race could be a hard-fought affair, with Tsai leading with 33.7% of support, compared with 28.9% for Han and 25.6% for Gou, according to a survey released Tuesday by the Apple Daily newspaper.

Since both Gou and Han support closer ties with China -- always Taiwan's most contentious wedge issue -- the Foxconn founder could complicate the KMT's bid to oust Tsai and her pro-independence Democratic Progressive Party. Tsai has been dogged by an increasingly assertive Beijing, which has been angered by her refusal to accept the Communist Party's bottom line that both sides belong to "one China."

"The KMT will be substantially impacted by Gou's declaration to run," said Stephen Tan, president of the Taipei-based Cross-Strait Policy Association. "Although Gou will run as an independent, his constituents have been mainly the 'blue' voters and the moderates whom KMT is working hard to seek for support."

Gou has continued to publicly flirt with the idea of a presidential bid despite losing the KMT primary to Han in July. The firebrand Kaohsiung mayor has become one the island's best-known -- and most divisive -- political leaders since his surprise win in the DPP's southern stronghold in November.

Han said he regretted Gou's move to withdraw from the KMT. Ma, the former president, and KMT Chairman Wu Den-yih were among several senior opposition figures who published advertisements in newspapers earlier Thursday urging Gou to support their nominee.

Gou built Foxconn from a maker of television knobs into a global powerhouse that is now Apple's biggest supplier and China's largest private employer. He also has ties to President Donald Trump, meeting the U.S. leader at the White House in May, weeks before stepping down as chairman of Hon Hai Precision Industry Co., Foxconn's main listed arm.

Shares in companies Gou controls rose after he quit the party Thursday, with FIH Mobile Ltd. surging more than 15% in Hong Kong and the group flagship Hon Hai rising 2% in Taipei.

Gou has been sending signals that he might mount an independent run for weeks, although he'll still need to collect around 280,000 signatures to get on the ballot. After assembling a campaign team, he confirmed last month that he was considering breaking from the KMT for a stand-alone bid.

"This conservative, hidebound party leadership is putting their own interests ahead of their party's and the party's interests ahead of the nation's," Gou's spokesman, Evelyn Tsai, told reporters Thursday. "Mr. Gou won't miss this party."