In protest to Taiwan's de facto U.S. embassy raising a Taiwanese flag on New Year's day, China has asked Washington to respect the "one China" policy, Reuters reported.

It was the first time the Taiwanese flag was raised in the U.S. in 36 years, since the U.S. started recognizing Beijing instead of Taiwan, according to Taiwan's China Post. 

"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," China's foreign ministry spokeswoman Hua Chunying said in a news briefing, asking Washington to "act with discretion when dealing with Taiwan-related issues."

Washington responded on Monday saying it was not given advanced notice about the flag-raising ceremony that occurred at the residence of Taiwan's representative to Washington, and said it was not consistent with U.S. policy, reported The Associated Press.

According to The Taipei Times newspaper, the Taiwanese representative to the U.S., Shen Lyu-shun, said his office had notified the White House before the New Year ceremony and even received approval on grounds that the ceremony was low-profile and not televised, AP reported.

State Department spokeswoman Jan Psaki said the U.S. remains committed to the one China policy and "nothing has changed" regarding the status of the U.S.-Taiwanese relationship and the U.S.

Since 1979, U.S. policy has recognized Beijing as representing China instead of Taiwan. Even though self-governing Taiwan broke off from the Chinese mainland following a 1949 civil war, China still regards Taiwan as part of its territory, which can make for a sensitive diplomatic situation in the U.S. Washington acknowledges China's claim over Taiwan, but considers the matter unsettled.

In December, Beijing protested a decision by President Barack Obama to authorize the sale of up to four Perry-class guided missile frigates to Taiwan, Reuters reported.