China's leadership is too "overwhelmed" with its internal problems to consider an invasion of Taiwan, President Tsai Ing-wen said in an interview with the New York Times.

China, which views democratically governed Taiwan as its own territory, has ramped up military pressure against the island over the past four years, leading to concerns of a conflict that would have global repercussions.

But Tsai, in a transcript of the New York Times DealBook Summit interview her office published on Thursday, said China had too many issues at the moment.

"Well, I think the Chinese leadership at this juncture is overwhelmed by its internal challenges. And my thought is that perhaps this is not a time for them to consider a major invasion of Taiwan," she said.

"Largely because the internal economic and financial as well as political challenges, but also, the international community has made it loud and clear that war is not an option, and peace and stability serves everybody's interests."

Asked about Tsai's comments, China's defence ministry said: "China will eventually and surely be reunified".

"The People's Liberation Army will take all necessary measures to firmly safeguard China's sovereignty and territorial integrity," ministry spokesperson Wu Qian told a monthly news briefing in Beijing.

Tsai and her government have repeatedly called for talks with China but been rebuffed, as Beijing views Tsai and the ruling Democratic Progressive Party (DPP) as separatists.

Tsai says only Taiwan's people can decide their future.

Taiwan is in the middle of campaigning for presidential and parliamentary elections to be held on Jan. 13. The DPP's Lai Ching-te, currently vice president, is the frontrunner to be Taiwan's next president according to opinion polls.

Tsai said it was "no secret" that China was trying to interfere in Taiwan's elections.

"But I think they're probably not particularly successful in their effort of trying to influence the election here. Primarily, because this is a democracy and people know that they have made their best decisions as to who is going to be the next leader of Taiwan," she added.

China's Taiwan Affairs Office on Wednesday stepped up its attacks on Lai and his running mate Hsiao Bi-khim, formerly Taiwan's envoy to the United States.

"Taiwan independence means war. The DPP pushing this dangerous independence double act will only poison the interests and well being of compatriots on the island," spokesperson Chen Binhua told a news conference.

Speaking to reporters in Taipei on Thursday, top China-policy maker Chiu Tai-san dismissed Beijing's criticisms.

"Honestly speaking, those comments show they don't even know what democratic politics and elections are," said Chiu, who heads Taiwan's Mainland Affairs Council.