China confirmed Tuesday it has conducted an anti-satellite weapons test but insisted it wasn't militarizing space, nearly two weeks after the event that alarmed the world and prompted questions about Beijing's motives.

Both the United States and Japan have expressed concern about the Jan. 11 test, in which China used a missile to shoot down one of its own old weather satellites. Both countries criticized it as a step toward militarizing outer space and demanded explanations from Beijing.

In China's first public comment about the test, Foreign Ministry spokesman Liu Jianchao said it has shown a "responsible attitude" by offering explanations to the U.S. and Japan and insisted Beijing has all along "upheld the peaceful use of outer space."

"China opposes the weaponization of space and any arms race," Liu said, adding that it has never and will not participate in any outer space arms race.

"The test is not targeted at any country and will not threaten any country," he said at a regular briefing.

Liu did not explain why China had not commented earlier on the test, which was likely carried out under the auspices of its highly secretive, military-dominated space program.

The Bush administration said it detected the test but kept it secret for a week while it weighed its significance. It was first reported in Aviation Week magazine last week.

"The United States believes China's development and testing of such weapons is inconsistent with the spirit of cooperation that both countries aspire to in the civil space area," National Security Council spokesman Gordon Johndroe said on Jan. 18. "We and other countries have expressed our concern to the Chinese."

Britain and Australia were among other countries also were concerned that debris caused by the test could scatter and strike other satellites orbiting the Earth.

Because China's weather satellites would travel at about the same altitude as U.S. spy satellites, analysts also said the test represented an indirect threat to U.S. defense systems.

Foreign Ministry officials told U.S. Assistant Secretary of State Christopher Hill about the test in a weekend meeting in Beijing.

Hill, who heads the State Department's East Asia bureau, told the Chinese they should be more transparent about their military activities and their defense budget to "avoid any sort of misunderstandings, not only with the United States, but other countries around the world," State Department spokesman Sean McCormack said Monday.

China is listed as a country of highest concern for the United States, along with North Korea and Iran, in potential for development of unconventional weapons.

While Beijing has worked with the United States to induce Pyongyang to dismantle its nuclear weapons program, it also maintains cordial diplomatic and trade relations with some of the world's most repressive countries including Sudan, Zimbabwe and Myanmar.

The test also comes as ties between China and Japan remain precarious because of ongoing disputes over territorial issues, use of maritime resources and interpretations of wartime history.

Chinese military modernization has been a key security concern for Tokyo, a top U.S. ally in Asia.

Beijing has repeatedly pledged peaceful development of its army — the world's largest — but has caused unease among its neighbors by announcing double-digit military spending increases nearly every year since the early 1990s.

It has spent heavily on beefing up its arsenal with submarines, jet fighters and other high-tech weapons.

A report issued last month by the State Council, China's cabinet, said the air force was giving priority to the development of new fighters as well as air and missile defense weapons.