The United States formally unveiled its new de facto embassy in Taiwan’s capital Taipei on Tuesday, signalling Washington’s strategic ties with the democratic, self-ruled island even as it faces tensions with China, reported Reuters.

The US switched diplomatic recognition to China in 1979 but maintains economic, political and security ties with Taiwan, according to AFP.

Senior officials from the US and Taiwan, including the island’s President Tsai Ing-wen, attended a ceremony held at the American Institute of Taiwan that was built at a cost of $250 million (Rs 1,663 crore), reported South China Morning Post.

Taiwan President Tsai Ing-wen said the new building was a reaffirmation of commitment to a “vital relationship” between the US and Taiwan. “The friendship between Taiwan and the US has never been more promising,” Tsai said, according to Reuters. “The great story of Taiwan-US relations remains to be filled with the efforts of those that will one day occupy this building.”

Marie Royce, a representative of the US government, said the office complex is a “symbol of the strength and vibrancy of the US-Taiwan partnership in the 21st century”.

Chinese Foreign Ministry spokesperson Geng Shuang said Beijing was “gravely concerned” with the inauguration of the building. “If any US official attends this activity, whatever their excuse may be, it violates the one China principle,” AFP quoted Geng as saying.

Taiwan governs itself democratically, but China considers the island nation an integral part of its territory, and relations remain strained. Beijing has been more hostile since Tsai was elected Taiwan’s president in 2016 because she refuses to recognise the “one China” policy.