NASA has lost 20% of its employees since Trump's return to the presidency.

NASA will lose about 3,900 employees as part of Donald Trump's plan to reduce federal staff, although the president remains determined that the US space agency will conduct manned missions to the Moon and Mars.

The aerospace agency said in a statement that approximately 3,000 employees have signed up for the second round of voluntary redundancy plans. In the first round, 870 workers agreed to leave the agency.

NASA's staff has shrunk from 18,000 to just over 14,000 since Trump's return to the White House, a reduction of more than 20 percent.

Agency employees who have joined the voluntary redundancy program will gradually leave their positions.

"Safety remains a top priority for our agency as we balance the need to become a more agile and efficient organization and work to ensure we remain fully capable of pursuing a golden age of exploration and innovation, including the Moon and Mars," NASA leadership explained.

The Trump administration's proposed budget for the agency emphasized returning humans to the Moon and conducting a manned mission to Mars for the first time, while drastically cutting science and climate programs.

The White House says it wants to focus resources on “beating China in the race to return to the Moon and put the first human on Mars.”

Beijing aims to make its first manned lunar landing in 2030.

NASA remains under the leadership of an acting administrator after the administration's initial choice to lead the agency, tech billionaire Jared Isaacman, backed by former Trump adviser Elon Musk, was rejected by the Republican president.