Donald Trump is backing a $20bn (£15bn) mission to build a base on the surface of the Moon – and perhaps beat China to it along the way.
Nasa has announced it has decided to abandon a proposal to have a station hanging in lunar orbit and instead establish a building on the surface.
The agency said it also intended to send a nuclear-powered spacecraft to Mars.
Jared Isaacman, who was appointed head of Nasa by the president in November, said plans were in place to send robotic landers and deploy a fleet of drones. They will pave the way for using nuclear power on the lunar surface in the next few years.
“This revised step-by-step approach to learn, build muscle memory, bring down risk, and gain confidence is exactly how Nasa achieved the near impossible in the 1960s,” he said, referring to the US Apollo programme.
He added: “Nasa is committed to achieving the near‑impossible once again, to return to the Moon before the end of President Trump’s term, build a Moon base, establish an enduring presence, and do the other things needed to ensure American leadership in space”.
The announcement represents a major shake-up of the current Artemis Moon programme and has raised questions about the future involvement of partners such as Japan, Canada and the European Space Agency.