Beijing, China - China urged the Trump administration on Tuesday to stop "preparing for war in outer space," after the US Space Force confirmed it had deployed weapons in orbit.

The US Space Force on Monday said it had deployed "on-orbit space control weapons capable of defending… against hostile adversary action," but did not provide specific details.

China's foreign ministry opposed the move, warning against the "weaponization of outer space, turning it into a battlefield, as well as an arms race."

"We urge the US side to stop expanding its military capabilities and preparing for war in outer space," Foreign Ministry Spokesperson Guo Jiakun told a news briefing.

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The US Space Force singled out China as a threat in its announcement, claiming that Beijing "develops and operates space and counter space capabilities as part of a military modernization strategy."

It also named Russia, another geopolitical rival, which it said "believes space supremacy will be a decisive factor in future conflicts."

The militarization of space is as old as the space race itself – as soon as the Soviet Union launched the world's first artificial satellite, Sputnik, into orbit in 1957, Washington and Moscow began exploring ways to fight a war in space.

The biggest worry was once about nuclear weapons in space, but the superpowers and other countries signed the Outer Space Treaty in 1967, banning weapons of mass destruction in orbit.

Since then, the US, China, Russia, and India have explored ways to fight in space outside of that treaty, including by targeting rivals' satellites, which are key for military communications, surveillance, and navigation.