Taiwan political veteran James Soong announced Thursday he would run for president, taking on two female candidates in an already dramatic battle and posing yet another headache for the beleaguered ruling Kuomintang (KMT).

It will be the fourth presidential bid by Soong, chairman of the pro-China People First Party (PFP), who is seen as an unpredictable figure in Taiwan having flip-flipped between being an ally and a foe of the KMT.

China policy will be at the centre of the leadership race as concern mounts over warming ties with the mainland, a major factor in the decline in public support for the Beijing-friendly KMT.

Taiwan split from China in 1949 after a civil war and is self-ruling, but Beijing still sees the island as part of its territory awaiting reunification -- by force if necessary.

Soong will run against the KMT's Hung Hsiu-chu and Tsai Ing-wen of the main opposition Democratic Progressive Party (DPP), which traditionally takes a sceptical approach towards China relations.

Tsai is currently the clear frontrunner, with Hung having to row back on her pro-unification message after a public backlash and criticism from her own party.

Soong poses a further threat to Hung as he appeals to the pro-China camp.

"Taiwan and China need to work together, not antagonise each other," Soong said in his candidacy speech in the capital Taipei Thursday.

"Maintaining the status quo is the biggest consensus we have in Taiwan right now."

He denied that he was entering the race to undermine any party and said that if elected he would ensure dialogue with opposition parties.

"A divided Taiwan cannot compete on the world stage," he told a hall full of supporters.

"Until the day the people have a government they can trust, I don't have a reason not to run."

Soong only took 2.77 percent of votes in the last election in 2012, which saw current president Ma Ying-jeou beat Tsai to the leadership.

He served in the KMT for decades -- starting as a secretary to then-president Chiang Ching-kuo -- before leaving the party in 2000 to run as an independent presidential candidate after failing to be nominated to represent the party.

Soong and then-KMT candidate Lien Chan lost to Chen Shui-bian of the DPP in a controversial election that put the opposition party in power for first time.

The KMT is currently under fire over changes made to the high-school curriculum which critics say promote a version of history favorable to mainland China.

Students have led protests in the past few months and occupied the ministry of education last week following the suicide of a young activist who opposed the curriculum changes.

Around 100 remain camped out in the ministry compound.

Thousands also rallied last year against a new trade pact with China in a student-led protest which occupied parliament for more than three weeks.

The KMT subsequently suffered its worst-ever defeat at local elections in November.