(CNN) Establishing President Donald Trump's sought-after Space Force could cost $12.9 billion over its first five years, according to an Air Force document obtained by CNN.

The Air Force estimates that the first year "additive costs" associated with establishing the new military branch in the 2020 fiscal year, including the creation of a headquarters, would amount to $3.32 billion.

The document also estimates that the Space Force will oversee some 13,000 personnel when it is officially launched.

In a memo accompanying the proposal, Air Force Secretary Heather Wilson calls on Congress to authorize and fund the establishment 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 September 14.

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