Billionaire tech investor Elon Musk's Space Exploration Technologies plans to sue the US Air Force, saying it should be allowed to compete in a satellite-launch market monopolised by the two biggest defence contractors.

"If we compete and lose, that is fine," he told reporters at the National Press Club in Washington. "But why would they not even compete it?"

Mr Musk's company, known as SpaceX, is trying to break the Lockheed Martin Corp.-Boeing joint venture's lock on military satellite launches, which have an estimated value of $US70 billion through 2030. Lockheed and Boeing are the military's biggest suppliers.

SpaceX, based in California, plans to file its suit Monday in the US Court of Federal Claims. It's seeking to reopen competition for a contract to the joint venture, United Launch Alliance LLC, for 36 rocket cores.

Advertisement

Bloomberg