China has protested to the United States after Taiwan’s de facto embassy in Washington hoisted a Taiwanese flag on New Year’s Day, calling on the United States to respect the “One China” policy, the foreign ministry said on Monday.

Taiwan’s China Post newspaper reported on Saturday that it was the first time the Taiwanese flag was raised in the United States in 36 years since the United States switched recognition from Taiwan to Beijing in 1979.

More than 100 people attended the ceremony at the Twin Oaks Estate in Washington last Thursday, including Taiwan’s top envoy to the U.S. Shen Lyushun, the China Post said, citing the Taipei Economic and Cultural Representative Office in Washington.

“We resolutely oppose the so-called flag-raising ceremony by Taiwan’s agency in the United States and have lodged solemn representations with the United States,” foreign ministry spokeswoman Hua Chunying told a daily news briefing.

Mainland China deems Taiwan a renegade province and has never ruled out the use of force to take it back, particularly if the island makes a move toward independence. China and Taiwan have been ruled separately since defeated Nationalist forces fled to the island at the end of a civil war with the Communists in 1949.

Hua called on the United States to abide by the ‘One China’ policy and “prudently and properly handle” any issues related to Taiwan so as to prevent similar incidents from happening again.

The flag-raising ceremony is the latest incident involving Taiwan to roil relations between the United States and China. Beijing said in December that it had lodged a protest with the United States after President Barack Obama signed into law legislation authorizing the sale of up to four Perry-class guided missile frigates to Taiwan.

While Taiwan and China have signed a series of landmark trade and economic agreements since 2008, political and military suspicions still run deep, especially in democratic Taiwan where many fear China’s true intentions.