The US has adopted a tough new policy aimed at protecting its interests in space and denying "adversaries" access there for hostile purposes.
The document outlines US military and commercial ambitions in space
The document - signed by President Bush - also says "freedom of action in space is as important to the United States as air power and sea power".
The document rejects any proposals to ban space weapons.
But the White House has said the policy does not call for the development or deployment of weapons in space.
However, some military experts warn that by refusing to enter into negotiations on space weaponry, the US is likely to fuel international suspicions that it will develop such weapons.
The 10-page strategic document states that the US national security "is critically dependent upon space capabilities, and this dependence will grow".
"The United States will preserve its rights, capabilities, and freedom of action in space... and deny, if necessary, adversaries the use of space capabilities hostile to US national interests," it says.
The document also sets out US commercial ambitions, saying it is committed to encouraging and facilitating a growing entrepreneurial space sector.
It is the first revision in US space policy for 10 years, and it is a forthright one, the BBC's Nick Miles in Washington says.
The Bush administration says there is no shift in its policy
It addresses concerns voiced in a 2001 Pentagon report that said technological advances would enable potential enemies to disrupt orbiting US satellites, our correspondent says.
Unclassified details of the policy published on the internet say space capabilities, including spy and other communication satellites, are essential for national security.
But the White House said the policy was not a prelude to putting weapons in orbit and that there was no shift in US policy.
"The notion that you would do defence from space is different from that of weaponisation of space. We're comfortable with the policy", White House spokesman Tony Snow said.
President Bush authorised the policy in August but it was not released until October.
During the Cold War, President Ronald Reagan proposed a defence shield using laser or particle beam technology to "intercept and destroy" incoming nuclear missiles.
The Strategic Defence Initiative, or "Star Wars" programme as it came to be known, was abandoned in 1993.