BEIJING, Sept. 22 (Xinhua) -- U.S. arms sales to Taiwan will harm peace and stability across the Taiwan Strait and the basic interests of people on both sides, said a statement from the State Council Taiwan Affairs Office Thursday.

The decision also violated the principles reached in the three Sino-U.S. joint communiques and broke the promise the U.S. has made to support peaceful development across the Strait, the statement said.

"We are strongly discontent and firmly oppose what the U.S. side has decided to do," the statement said.

The U.S. administration announced Wednesday a new arms package worth 5.85 billion U.S. dollars to Taiwan, including the so-called "upgrading" of F-16A/B fighter jets.

Since May, 2008, cross-Strait relations have developed peacefully and gained support from people on both sides as well as from the international community, the statement said.

The situation across the Strait has maintained "a hard-earn stability", it said.

Taiwan has repeatedly exaggerated the military threats from the mainland. This will hold back the development of cross-Strait relations, it said.

"We hope that the Taiwan side can get a clear picture of the current situation and not step up confrontation across the Strait or make any moves that might harm the stability of the region and affect peaceful development across the Strait," the statement said.