In an emailed statement, NASA said around 3,000 employees took part in the second round of its deferred resignation program, which closed late Friday.

Combined with the 870 who joined the first round and regular staff departures, the agency's civil servant workforce is set to drop from more than 18,000 before Trump took office in January to roughly 14,000 -- a more than 20 percent decrease.

Those leaving the National Aeronautics and Space Administration on the deferred resignation program will be placed on administrative leave until an agreed departure date. An agency spokesperson said the figures could shift slightly in the coming weeks.

"Safety remains a top priority for our agency as we balance the need to become a more streamlined and more efficient organization and work to ensure we remain fully capable of pursuing a Golden Era of exploration and innovation, including to the Moon and Mars," the agency said.

Earlier this year, the Trump administration's proposed NASA budget put a return to the Moon and a journey to Mars front and center, slashing science and climate programs.

The White House says it wants to focus on "beating China back to the Moon and putting the first human on Mars." China is aiming for its first crewed lunar landing by 2030, while the US program, called Artemis, has faced repeated delays.

NASA is still run by an acting administrator after the administration's initial pick to lead the agency, tech billionaire Jared Isaacman -- endorsed by former Trump advisor Elon Musk -- was ultimately rejected by the Republican president.