The US has asked China to explain its intentions after Beijing reportedly carried out a weapons test in space last week.
The missile was reportedly launched near Xichang Space Centre
It is thought the Chinese used a ground-based, medium-range ballistic missile to destroy a weather satellite.
The US state department said it did not want the "militarisation of space".
China's foreign ministry refused to confirm or deny the report but said Beijing was opposed to "any form of arms race".
The test, if confirmed, would be the first known satellite intercept for more than 20 years.
US state department spokesman Tom Casey said the Bush administration had made clear to China its opposition to such tests.
In space programmes, he said "small things can cause very big problems".
Mr Casey said the tests could "produce extensive amounts of space debris [that] have the potential for disturbing or accidentally disrupting communications satellites".
White House deputy press secretary Dana Perino said the Chinese had not yet responded.
"We do want co-operation on a civil space strategy, so until we hear back from them, I don't have any more to add," she said.
Mr Casey said the US had "no plans or intentions" to engage in space arms tests.
However, Washington has recently opposed international calls to end such tests - and the US is known to be researching such "satellite-killing" weapons.
The BBC's Jonathan Beale, in Washington, says the US has been cautious in its criticism, not least because it wants good relations with China, and has played down talk of an arms race.
Earlier, China's foreign ministry spokesman Liu Jianchao said: "I can't say anything about the reports. I really don't know."
CHINA IN SPACE
China first launched a manned space mission in 2003 - the third nation to do so after the US and Russia
Chinese astronauts aim to perform a spacewalk as early as next year
Until now, the US and Russia have been the only nations to shoot down space objects
China insists its space programme is of no threat, but other nations are wary
China says it spends $500m on space projects. NASA is due to spend $17bn in 2007
But he added: "China advocates the peaceful use of space and opposes the weaponisation of space, and also opposes any form of arms race."
Australia and Japan have been among the countries joining criticism of the reported test.
Japanese Prime Minister Shinzo Abe said he had asked China for an explanation and said nations "must use space peacefully".
Australian Foreign Minister Alexander Downer said Australia did not want to see "some sort of spread... of an arms race into outer space".
The US National Security Council had confirmed an article in the magazine American Aviation Week and Space Technology, which reported that the test had taken place.
The report said a Chinese Feng Yun 1C polar orbit weather satellite was destroyed by an anti-satellite system launched from or near China's Xichang Space Centre on 11 January.
The test is thought to have occurred at more than 537 miles (865km) above the Earth.