It would overturn a 1996 directive signed by President Clinton, which drew the line at using satellites to support military operations, arms control and non-proliferation pacts.

Scott McClellan, Mr Bush’s spokesman, said that US space policy needed to be updated because in the past nine years there had been “a number of domestic and international developments that have changed the threats and challenges facing our space capabilities”.

In an apparent reference to China, but without mentioning it by name, Mr McClellan said: “There are countries that have taken an interest in space. And they have looked at technologies that could threaten our space systems. And so you obviously need to take that into account when you’re updating the policy.”

The Pentagon has prepared a draft presidential directive that would allow the US Air Force to begin planning how best to field weapons in space. Mr McClellan said that the Administration believed “in the peaceful exploration of space” and would continue to abide by treaties to which it was a signatory.

Critics said that any move towards militarising space would lead to a potentially damaging arms race. The plans also carry implications for the American budget deficit.

Last month the USAF launched an $80 million (£43.5 million) experimental micro-satellite that could be used to disrupt an enemy’s communications and reconnaissance satellites. The XSS11, launched from Vandenberg Air Force base in California on a 12 to 18 month mission can provide 200 pictures a day or give a live feed during US operations.

Others at the planning stage are more aggressive, according to The New York Times. The Global Strike programme envisages a military spacecraft carrying precision-guided weapons capable of striking halfway round the world in 45 minutes. Pentagon chiefs have told Congress that it would offer US commanders “an incredible capability”, allowing them to destroy centres or missile bases around the world.

Another USAF programme is the “Rods from God”, in which cylinders of tungsten, titanium or uranium would be launched from space to strike ground targets at speeds of 7,200mph.

Donald Rumsfeld, the US Defence Secretary, promoted this new phase in space weapons in 2001 when a commission that he headed recommended that the Pentagon “ensure that the President will have the option to deploy weapons in space”. Three years later the USAF believes that it has done the planning necessary to move to the next stage.

One of the most controversial acts of the early Bush presidency has helped to clear the way. Under the 1972 Anti-Ballistic Missile Treaty between the United States and the Soviet Union, Washington and Moscow agreed not to place weapons in space. Mr Bush unilaterally withdrew from the treaty to allow the Pentagon to pursue the missile defence umbrella first championed by President Reagan.

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