Twin Oaks Estate in Washington seen on snowy Tuesday. A ceremony of raising Taiwan flag here on January 1 drew protest from the Chinese government and disappointment expressed by the US government. Chen Weihua/China Daily

The United States expressed disappointment Tuesday over a Jan 1 ceremonial raising of Taiwan's flag in the Twin Oaks Estate in Washington.

State Department spokeswoman Jen Psaki said at a daily briefing on Tuesday: "We're disappointed with the action.The flag-raising ceremony violated our longstanding understanding on the conduct of our unofficial relations."

Psaki emphasized that the US has a robust set of cultural relations with Taiwan, but does not have diplomatic relations.

Taiwan's Central News Agency reported Jan 2 that the flag-raising ceremony was held Jan 1 at Twin Oaks for the first time in the last 36 years since the US established diplomatic ties with the People's Republic of China.

The story quoted Shen Lyushun, Taiwan's representative to the US, as saying that it was meaningful to be able to hold a flag-raising ceremony again at Twin Oaks, an 18-acre estate in Washington's Cleveland Park neighborhood.

The Chinese government has protested against the ceremony being held in Washington.

"We are resolutely opposed to the so-called flag-raising ceremony staged by Taiwan's office in the US and have lodged solemn representations with the American side," Chinese Foreign Ministry spokeswoman Hua Chunying said at a daily briefing in Beijing on Monday.

"The Chinese side requests the American side to adhere to the one-China policy and the principles established by the three China-US joint communiqués, act with discretion when dealing with Taiwan-related issues and avoid the recurrence of a similar incident," she said.

Psaki said Tuesday that US officials in Washington and Taipei are talking to Taiwan authorities about the issue.

She reiterated that it was inconsistent with US policy, and the US side was unaware of the event in advance. She emphasized that the Twin Oaks is the compound of Taipei's representative and not a private person's home.