President Trump will sign a policy directive Monday setting in motion the return of U.S. astronauts to the moon.

American astronauts visited the moon six times in the late 1960s and early '70s, beginning with Neil Armstrong’s first steps in 1969 and ending with Apollo 17 in 1972.

Trump will instruct the NASA administrator “to lead an innovative space exploration program to send American astronauts back to the Moon, and eventually Mars,” White House spokesman Hogan Gidley said in a statement.

“The [p]resident listened to the National Space Council’s recommendations and he will change our nation’s human spaceflight policy to help America become the driving force for the space industry, gain new knowledge from the cosmos, and spur incredible technology,” Gidley said.

Trump’s orders will be contained in a document called Space Policy Directive 1, or SPD-1.

Gidley’s statement did not offer a timeframe for humans returning to the moon or visiting Mars for the first time. No other country has sent people to the moon, but China has said it wants to send its people to the moon in the next 15 or 20 years.