China’s foreign ministry on Thursday condemned a meeting in California between Taiwan’s leader and the US House Speaker as “acts of collusion” and said it would defend its sovereignty, according to the Xinhua news agency.

“China firmly opposes and strongly condemns the acts,” China’s foreign ministry spokesperson said, according to the official state news agency.

“In response to the seriously erroneous acts of collusion between the United States and Taiwan, China will take resolute and effective measures to safeguard national sovereignty and territorial integrity.”

House Speaker Kevin McCarthy hosted Tsai Ing-wen in California on Wednesday, becoming the most senior US figure to meet a Taiwanese leader on US soil in decades and stressed the need to speed up arms deliveries to Taiwan in the face of increasing threats from China.

A separate statement issued by Foreign Affairs Committee of the National People’s Congress on Thursday, carried by Xinhua, said McCarthy’s actions had “seriously broken the commitment made by the United States to China on the Taiwan question.”

China claims democratically governed Taiwan as its own territory, a position the government in Taipei strongly contests. Washington switched diplomatic recognition from Taiwan to Beijing in 1979.