A U.S. destroyer and a Canadian frigate navigated through the hotly contested waters Sunday, approximately one week after the People’s Republic of China scrambled air and naval forces around the island of Taiwan.

The U.S. Navy’s 7th Fleet said the quick trip through the strait “demonstrated the United States’s and Canada’s commitment to upholding freedom of navigation for all nations as a principle.”

Chinese officials were quick to complain that the ships had illicitly navigated through its waters.

“The actions of the U.S. and Canada have disturbed the situation and undermined peace and stability across the Taiwan Strait,” said Senior Captain Li Xi, People’s Liberation Army Eastern Theater Command spokesman.

The mainland claims sovereignty over Taiwan, also known as the Republic of China, and the strait separating it from the continent’s Eastern coast.

“The international community’s navigational rights and freedoms in the Taiwan Strait should not be limited,” the U.S. Navy’s 7th Fleet said in a statement defending the legality of its action.

When asked about the situation at a Monday press conference, Chinese foreign ministry spokesman Lin Jian deferred to the Eastern Theater Command’s statement but reiterated the Chinese Communist Party‘s belief that “Taiwan is an inalienable part of Chinese territory.”

“The Taiwan question is not about freedom of navigation but about China’s sovereignty and territorial integrity,” Lin said. “We firmly oppose any act of provocation under the pretext of freedom of navigation that threatens China’s sovereignty and security.”

Chinese military officials launched a large-scale war game one week ago in which fighter planes, warships, and an aircraft carrier swarmed around Taiwan in a mock invasion that spooked the island and its allies.

The aggressive flex of military power was triggered by Taiwanese President Lai Ching-te’s National Day speech, in which he said China needed to respect the sovereignty of the island territory.

“The Republic of China and the People’s Republic of China are not subordinate to each other. On this land, democracy and freedom are growing and thriving,” Lai said. “The People’s Republic of China has no right to represent Taiwan.”

Chinese leaders and state outlets declared the Chinese military drills a direct response to Lai’s statements contesting the mainland government’s claims of sovereignty over the island.

“We are willing to exert utmost sincerity and make every effort to strive for the prospect of peaceful reunification, but we will never promise to renounce the use of force, nor will we leave any room for ‘Taiwan independence,’” Chinese Defense Ministry spokesman Wu Qian said following the drills.