The Pentagon said the ground-based, ultra-high-frequency radar would boost Taiwan's ability to "identify and detect ballistic missiles, cruise missiles and air-breathing target threats," or weapons that operate in the Earth's atmosphere.

The United States acknowledges China's claim to Taiwan, but makes no statement about Taiwan's status. It remains the self-ruling island's main arms supplier, major trade partner and biggest ally despite last month's controversial re-election of pro-independence President Chen Shui-bian.

"We have always opposed US sales of advanced weapons to Taiwan," Chinese Foreign Ministry spokesman Kong Quan told reporters in Beijing.

"Especially under the current complicated and sensitive situation across the Taiwan Strait, we ask the United States to be faithful to what it says and abide by its promises and not send the wrong signal to Taiwan's independence (seekers)."

For his part, Chen urged the United States to take a "more active, constructive" role in encouraging dialogue between Taiwan and China, diplomatic and ideological foes since the end of the Chinese civil war in 1949.