Chinese President Xi Jinping, in his annual New Year's Eve address, reiterated his claim that Taiwan would "surely be reunified" with China.
His message comes ahead of Taiwan's crucial 13 January elections that will determine the island's cross-strait policy for the next four years.
He also struck a stronger tone than last year's message, where he spoke of Taiwan being part of the "same family".
China has ramped up military pressure on Taiwan ahead of the elections.
It sees the self-ruled island of 23 million as a breakaway province that will eventually be under Beijing's control. Taiwan considers itself distinct from the Chinese mainland, with its own constitution and democratically elected leaders.
Separately, Taiwan's President Tsai Ing-wen said in her New Year's address that the island's relations with China must be decided by the "will of the Taiwanese people". Her government has repeatedly warned that Beijing is trying to interfere in the election, where a new president and government will be chosen.
Taiwan's Kuomintang party (KMT) has traditionally favoured warmer ties with Beijing - though it denies being pro-China. The KMT's main rival, Ms Tsai's Democratic Progressive Party (DPP), has ruled Taiwan for the past eight years and takes a stronger line towards China - insisting it is sovereign and not a part of China.
Mr Xi's latest comments are in line with China's long-standing policy towards unification, but the message struck a more strident tone than the one Mr Xi gave last year, where he called "people on both sides of the Taiwan Strait... members of one and the same family".
The issue of Taiwan has also strained relations between the US and China, with the latter condemning any perceived support from Washington for Taipei. Beijing has said that it "reserves the option of taking all necessary measures" against outside forces that interfere with peaceful unification.
But both countries marked the new year with a positive message, with Mr Xi and US President Joe Biden exchanging congratulatory messages on Monday.
Mr Xi noted that "adhering to mutual respect, peaceful coexistence, and win-win cooperation is the correct way for China and the United States to interact", according to Reuters, which cited Chinese state media outlet CCTV.
China and Taiwan: The basics
- Why do China and Taiwan have poor relations? China sees the self-ruled island as a part of its territory and insists it should be unified with the mainland, by force if necessary. But Taiwan sees itself as distinct from the mainland
- How is Taiwan governed? The island has its own constitution, democratically elected leaders, and about 300,000 active troops in its armed forces
- Who recognises Taiwan? Only a few countries recognise Taiwan. Most recognise the Chinese government in Beijing instead. The US has no official ties with Taiwan but does have a law which requires it to provide the island with the means to defend itself
