The Chinese mainland will "never leave any room for separatist activities for 'Taiwan independence' in all forms," and would take resolute measures to thwart any outside interference, a mainland spokesperson said on Friday night.

Zhu Fenglian, spokeswoman for the Taiwan Affairs Office of the State Council, said in a news release "the complete reunification of the motherland must be and can be definitely achieved".

The spokesperson also urged the United States to earnestly abide by the one-China principle and the three China-US joint communiques and prudently handle Taiwan-related affairs.

Zhu made the remarks as Tsai Ing-wen, the leader of the island, who returned after her "transit" in the US, during which she met with US House Speaker Kevin McCarthy in California.

The mainland official pointed out what Tsai did during her "transit" made it clear the trip was an excuse, and a provocation to seek independence by relying on the US.

"For some time, the DPP authorities have been challenging the one-China principle by, for its own political gain, acting as a pawn of the US attempting to contain China and spreading 'Taiwan independence' rhetoric, ignoring the interests of the Taiwan people to cooperate with the US in decoupling with China," she said.

Zhu said the DPP authorities would only "push Taiwan to the danger of war and bring grave catastrophes to our compatriots in Taiwan" in the end, given the DPP authorities' increasing efforts to "court and infiltrate" the US Congress and buy arms with the hard-won money of the people of the island.