BEIJING, June 13 (Xinhua) -- A Chinese mainland spokesperson Wednesday expressed firm opposition against official contact between the United States and Taiwan "in any form."

"The United States should adhere to the one-China principle and the three joint communiques between China and the United States so as not to undermine bilateral ties and peace and stability in the region," said Ma Xiaoguang, spokesperson with the State Council Taiwan Affairs Office, commenting on a U.S. official attending the dedication ceremony of the new office complex of the American Institute in Taiwan Tuesday.

"Taiwan's Democratic Progressive Party administration will only further damage cross-Strait relations by implicating foreign powers," Ma said. "The Taiwan issue, which is vital to China's sovereignty and territorial integrity, remains the most important and sensitive issue in China-U.S. relations.

Ma urged the U.S. side to handle this issue with caution.