The Chinese military used a ground-based missile to hit and destroy one of its aging satellites orbiting more than 500 miles in space last week — a high-stakes test demonstrating China's ability to target regions of space that are home to U.S. spy satellites and space-based missile defense systems.

The test of anti-satellite technology is believed to be the first of its kind in two decades by any nation and raised concerns about the vulnerability of U.S. satellites and a possible arms race in space.

The Chinese test, first reported online by the magazine Aviation Week and Space Technology, comes at a time of heightened tensions between the United States and China over space. China is leading an effort in the United Nations to set up an international conference to address what many consider to be an imminent space arms race. The United States has opposed the idea, arguing that it is not needed because there is no arms race in space. The Bush administration nevertheless released an updated national space policy last fall that strongly asserted an American right to defend itself in space against any actions it considers hostile.

The day the test was conducted, the chiefs of major U.S. intelligence agencies presented their annual threat assessments to Congress. Neither China's anti-satellite program nor its general push toward space weapons was mentioned during the public hearing or anywhere in the written testimonies of the director of national intelligence, the director of the Pentagon's intelligence agency or the CIA director.

The most obvious reason for China’s test at this time would be to push the United States, and particularly the new Democrat-controlled Congress, into signing a formal treaty banning the use of anti-satellite weapons. Otherwise, any ground-based missile — in a silo, on a submarine, or even on a test range — would have to be considered a potential anti-satellite weapon.

The United States, while asserting that it does not possess and is not developing such a weapon, has become diplomatically isolated on this issue in recent years by proclaiming that such a treaty is undesirable because it isn’t needed — because there has not been any “arms race in space” that would require a formal agreement. The Chinese test trumps that excuse.

The political response has been predictable, and probably just what China intended. For example, Rep. Edward Markey, D-Mass., told The Washington Post that the Chinese action makes it essential that the administration begin negotiations to stop any possible space arms race.