Washington: Two former top Nasa officials unveiled plans on Thursday to sell manned flights to the moon by the end of the decade, in an announcement 40 years after the last human set foot there.

Spaceflight, long the province of national governments, has moved toward increased commercialization in recent years, with private companies for the first time successfully launching rockets into orbit.

The US space agency, in the hopes of keeping costs down, even retired its space shuttles in 2011. NASA has instead paid for space on Russian craft to get people and supplies to the International Space Station — and, more recently, on one built and operated by SpaceX that carried just cargo.

But with ever shrinking budgets, manned flights beyond Earth’s orbit have been put on hold, with the US space agency relying on robots to do its exploring of the rest of the solar system.