But two events in the past four years - a 2007 Chinese anti-satellite weapon test and a 2009 crash-in-orbit of two satellites - put so much new junk in space that everything changed, the report said.

For several years, the Russians and Chinese have been trying to push a treaty to ban space weapons.

China signalled yesterday that its first missile strike against an orbiting satellite was intended to force the US into talks aimed at abolishing weapons in space.