The strategy document was the first since President Donald Trump announced the creation of the new Space Force military arm in December.

"China and Russia present the greatest strategic threat due to their development, testing, and deployment of counterspace capabilities," it said.

"China and Russia each have weaponized space as a means to reduce US and allied military effectiveness and challenge our freedom of operation in space."

The strategy stressed that the US would strive to maintain superiority in space, in particular protecting GPS satellites on which the military as well as the emergency services, transport and even financial services depend.

China is investing billions of dollars in space and puts many satellites in orbit. In 2007, Beijing also successfully tested a surface-to-air missile strike against a satellite, according to the Pentagon.

Russia plans a test launch of its Angara heavy carrier rocket later this year, and is pressing ahead with the development of its new intercontinental ballistic missile, the Sarmat.

In 2018, President Vladimir Putin boasted that the Sarmat was one of the new Russian weapons that could render NATO defenses obsolete.

The US, which is reviving its space exploration program, recently celebrated its first crewed spacecraft flight in nearly a decade, sending two astronauts to the International Space Station in a privately-built capsule.

The strategy document underlined that the US would "promote burden-sharing with our allies and partners."