President Trump’s plan to create a Space Force could cost nearly $13 billion during its first five years alone, CNN reported Monday after obtaining an Air Force document describing the costs.

The document also estimated that the Space Force would include an additional 13,000 members when it is officially launched.

In a memo accompanying the proposal, Air Force Secretary Heather Wilson called on Congress to approve the creation of a Space Force headquarters in the 2020 fiscal year.

“This would build the foundation of the new department first, allowing us to transfer personnel and programs in FY21 after Congressional approval,” she wrote in a memo dated Sept. 14, the network reported.

Wilson also pushed back on a recent Pentagon proposal to create a senior civilian defense post to oversee the Space Force, saying that did not conform with Trump’s plan to create a new branch of the military.

“Establishing an Assistant Secretary of Defense for Space or new defense bureaucracy, or moving programs to a temporary holding organization, in not in line with the President’s intent,” Wilson wrote.