China has ramped up its language on Taiwan as the Communist Party is raising the pressure on the country.
It comes as its president-elect Lai Ching-te is currently preparing to take office in May.
Beijing has long claimed the island as part of its territory and has threatened to take it by force if Taipei resists submitting to its control indefinitely.
However, Taiwan's government says China has no right to claim to represent the island's people on the international stage and that as the People's Republic of China has never ruled Taiwan, its sovereignty claims are void.
Lai Ching-te has previously been criticised by Beijing, who have called him a dangerous separatist. Lai has repeatedly offered talks with China but has been rebuffed.
China's official Xinhua news agency said the ruling Communist Party's fourth-ranked leader, Wang Huning, held a two-day meeting on this year's Taiwan-related work which ended on Friday.
It cited Wang as saying China "must resolutely combat the division of Taiwan independence, contain interference from external forces, firmly support the patriotic and reunification forces on the island, unite Taiwan compatriots, and maintain peace and stability in the Taiwan Strait."
He added that China must "further grasp the strategic initiative to achieve the complete unification of the motherland."
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Expert on cross-Strait relations at Tamkang University in Taipei Chang Wu-yueh told Financial Times: "Previous statements only pledged to ‘resolutely oppose’ Taiwan independence, but now they are using ‘fight’.
"Last year’s language was limited to mentions of 'peaceful development' but now they have added mentions of pushing for unification."
Neither government recognises the other.
President Xi Jinping told Joe Biden at a summit last year that if the US was committed to "one China", it should support peaceful unification of the two sides of the Taiwan Strait.
"This is a a demand that goes much further than Washington’s pledge not to support Taiwan independence."
Chang added: "In the past, they would only talk about the 'one-China principle' but now they have rolled it all into one with the push for unification."
Mao Zedong proclaimed the founding of the People's Republic in Beijing on October 1, 1949, after a bloody civil war.
The defeated Republic of China government fled to Taiwan at the end of 1949, and that remains the island's formal name.
