BEIJING  China announced a further sharp increase in military spending on Tuesday, a day after the United States renewed its warning that a lack of openness surrounding the rapid buildup of China’s armed forces posed a threat to stability in Asia.

China’s military budget for 2008 will increase by 17.6 percent to 417.8 billion yuan, or about $58.8 billion, Jiang Enzhu, spokesman for the National People’s Congress, China’s legislature, said at a news conference.

This follows a 17.8 percent increase in 2007.

Military experts in the United States and elsewhere say Beijing’s real military spending is at least double the announced figure. But even if it was double, China’s yearly military budget would still be only about one-fourth the size of the Pentagon’s.

Before the annual legislative session, which begins Wednesday, Mr. Jiang also said the situation in the Taiwan Strait was “grim and complex,” and called on the Taiwanese president, Chen Shui-bian, to halt what Beijing described as unacceptable moves toward independence. China considers the island of Taiwan a breakaway province.