US President Donald Trump is sending astronauts back to the Moon.

He signed a Space Policy Directive 1 at the White House on Monday, which NASA says is "a change in national space policy" that provides for a US-led, integrated program with private sector partners for a human return to the Moon.

This is set to be followed by missions to Mars and beyond.

The policy calls for NASA to "lead an innovative and sustainable program of exploration with commercial and international partners to enable human expansion across the solar system and to bring back to Earth new knowledge and opportunities."

The effort is set to more effectively organise government, private industry, and international efforts toward returning humans on the Moon.

It will also lay the foundation that will eventually enable human exploration of Mars.

"The directive I am signing today will refocus America’s space program on human exploration and discovery," President Trump said.

"It marks a first step in returning American astronauts to the Moon for the first time since 1972, for long-term exploration and use.

"This time, we will not only plant our flag and leave our footprints - we will establish a foundation for an eventual mission to Mars, and perhaps someday, to many worlds beyond."

Returning humans to the Moon

The policy grew from a unanimous recommendation by the US National Space Council, chaired by Vice-President Mike Pence, after its first meeting October 5th.

In addition to the direction to plan for human return to the Moon, the policy also ends NASA’s existing effort to send humans to an asteroid.

Mr Trump revived the National Space Council in July to advise and help implement his space policy with exploration as a national priority.

Among other dignitaries on hand for the signing, were NASA astronauts Senator Harrison 'Jack' Schmitt, Buzz Aldrin, Peggy Whitson and Christina Koch.

NASA says work toward the new directive will be reflected in NASA's 2019 budget.

Acting NASA administrator Robert Lightfoot said: "NASA looks forward to supporting the president’s directive strategically aligning our work to return humans to the Moon, travel to Mars and opening the deeper solar system beyond.

"This work represents a national effort on many fronts, with America leading the way.

"We will engage the best and brightest across government and private industry and our partners across the world to reach new milestones in human achievement."

A piece of Moon rock was brought to the White House as a reminder of the exploration history.

Lunar sample 70215 was retrieved from the Moon's surface and returned by Mr Schmitt’s Apollo 17 crew.

Lunar Sample 70215 was retrieved from the Moon's surface and returned by NASA's Apollo 17 crew | Image: NASA

Apollo 17 was the last Apollo mission to land astronauts on the Moon and returned with the greatest amount of rock and soil samples for investigation.

The sample is a basaltic lava rock similar to lava found in Hawaii. It crystallized 3.84 billion years ago when lava flowed from the Camelot Crater.

During the six Apollo surface missions from 1969 to 1972, astronauts collected 2,196 rock and soil samples weighting 842 pounds.