The spokesperson called on Washington to stop upgrading relations with Taiwan while reiterating China's readiness to take "strong and resolute measures" to defend the country's sovereignty.
On Wednesday, Taiwanese President Tsai Ing-wen met with US House Speaker Kevin McCarthy and other lawmakers in Los Angeles, California, during her transit trip to the country.
"The United States acting with Taiwan to connive at 'Taiwan independence' separatists’ political activities in the United States, conduct official contact with Taiwan and upgrade the substantive relations with Taiwan, and frame it as a 'transit.' This is a serious violation of the one-China principle and the provisions of the three China-US joint communiqués. It seriously infringes upon China’s sovereignty and territorial integrity and sends an egregiously wrong signal to the 'Taiwan independence' separatist forces. China firmly opposes and strongly condemns it," the spokesperson said in a statement on the website.
The spokesperson noted that "the Taiwan question is at the core of China’s core interests and the first red line," which Washington must not cross, adding that "the pursuit of 'Taiwan independence' will lead nowhere," and that Beijing will take "strong and resolute measures to defend our sovereignty and territorial integrity."
Beijing called on Washington to stop official exchanges with Taiwan and stop upgrading relations with the island, the spokesperson added.
"We once again urge the United States to adhere to the one-China principle and the provisions of the three China-US joint communiqués, act on the US leader’s assurances of not supporting 'Taiwan independence' and not supporting 'two Chinas' or 'one China, one Taiwan,' stop at once any form of official exchanges with Taiwan, stop upgrading substantive relations with Taiwan, stop creating factors that could cause tensions in the Taiwan Strait, stop containing China by exploiting the Taiwan question, and not go further down the wrong and dangerous path," the statement read.
Chinese Foreign Ministry spokeswoman Mao Ning said on Tuesday that Beijing firmly opposed the meeting, which it believes contradicts the one-China principle and undermines the country's sovereignty. China launched military patrols in two areas of the Taiwan Strait in an apparent response to the meeting in California.