Luxembourg-based satellite operator SES said on Wednesday it had signed up to launch three more satellites with the privately-owned SpaceX company.

The amount of the contract with the company that aims to cut the price of satellite launches was not disclosed.

SES, which has traditionally used Ariane rockets, gave the start-up its first contract to launch a geostationary satellite last year, and is scheduled for launch in 2013.

"This new contract is testimony to our belief in SpaceX's product and technical abilities," SES chief exec Romain Bausch said in a statement.

"It also confirms SES' priority for diversification of launch service providers and for securing timely access to space," he added.

All four launches will be on on SpaceX's Falcon 9 or Falcon Heavy rockets.

California-based SpaceX, owned by billionaire Internet entrepreneur Elon Musk who co-founded PayPal, scored a major success earlier this year when its cargo vessel linked with the International Space Station and returned to Earth.

SES operates a fleet of 51 geostationary satellites providing satellite communications services to broadcasters, telecommunications operators, and governmental organisations.