Foreign Ministry spokesman Liu Jianchao said in a statement Saturday that the arms sale would interfere in China's internal affairs and national security.
He says the Chinese government and people strongly oppose the sale, and that it would harm relations between China and the United States.
The U.S. government announced the package in a notification to Congress on Friday. It includes Apache helicopters and Patriot III anti-missile missiles.
The State Department said lawmakers (who were expected to leave Washington Friday to campaign for November elections) have 30 days to comment on the proposed sale. Without objections, the deal is completed.
The arms package enjoys support among senior lawmakers.
China, however, vehemently opposes the deal. Beijing claims the island as its territory and threatens to invade should the self-governing island ever formalize its de facto independence.
Taiwan relies on U.S. weapons to keep pace with China's massive arms buildup across the Taiwan Strait. U.S. arms sales to Taiwan are a sensitive matter because any dispute between China and Taiwan could ensnare the United States, Taiwan's most important ally and largest arms supplier. Washington shifted its recognition as China's official government from Taipei to Beijing in 1979, but it remains committed to Taiwan's defense and has hinted it could come to the island's aid if China should attack.
U.S. caution about selling arms to Taiwan reflects China's growing economic and political clout. The Bush administration needs China's help in a host of international efforts, including attempts to confront Iranian and North Korean nuclear programs.
This year's U.S. Defense Department report on China's military said Beijing continues its huge military buildup opposite Taiwan, further pushing the balance of power between the two rivals toward the mainland's favor.