China has reacted sharply to the meeting between Taiwan President Tsai Ing-wen and US House Speaker Kevin McCarthy, warning that Beijing will take "strong and resolute measures."

China's foreign ministry spokesperson Mao Ning made the remarks at a news conference on Thursday.

She criticized Washington for acting with Taiwan to "connive" at what she called "Taiwan independence separatists' political activities in the United States." She said China firmly opposes the US upgrade of its "substantive relations" with Taiwan and framing it as a "transit."

The spokesperson said this is a "serious violation of the one-China principle."

She added, "China will take strong and resolute measures to defend our sovereignty and territorial integrity."

Tsai met with McCarthy in California on Wednesday on her way back to Taiwan after visiting two Central American countries.

McCarthy said after the meeting that the bond between the US and Taiwan had never been stronger. He said it is critical to maintain economic freedom, peace and stability in Asia.

Tsai said, "The peace that we have maintained and the democracy that we have worked hard to build are facing unprecedented challenges."

She said the presence and unwavering support of US lawmakers reassure the people of Taiwan that they are not isolated.