China threatened to retaliate if US House speaker Kevin McCarthy meets Taiwan President Tsai Ing-wen during her planned transit of the United States, saying any such move would be a "provocation".

Tsai (above) is due to depart today for a trip to Guatemala and Belize that will see her transit through New York and Los Angeles.

Sources have said she plans to meet McCarthy during the California transit although there has been no official confirmation.

"If she contacts McCarthy, it will be another provocation that seriously violates the one-China principle, harms China's sovereignty and territorial integrity, and destroys peace and stability in the Taiwan Strait," Zhu Fenglian, spokesperson of China's Taiwan Affairs Office told a news conference today.

"We firmly oppose this and will definitely take measures to resolutely fight back."

- Reuters