The Pentagon appeared to throw cold water on President Trump’s plans for an independent “Space Force” Tuesday after the acting defense secretary said it should be “as small as possible” and be part of the Air Force.

“It’s going to be small, as small as possible footprint, that’s why I recommended it sits underneath the Air Force,” Pat Shanahan said in his first public comment on the plan.

Trump has touted the creation of a Space Force as a separate, sixth branch of the US military, arguing that it was necessary to counter Russia’s and China’s efforts to weaponize space with killer satellites and other technology.

But Shanahan’s plan would give it a much less prominent role in the military.

Pentagon brass were still putting the final touches on a Space Force legislative proposal for Congress, which will have the final say, while the White House is preparing an update on the plan for Trump, Politico reported.

But Democrats and some Republicans are wary of creating a new branch of the military because of the costs and added bureaucracy.

Trump’s Space Force could cost nearly $13 billion during its first five years alone, according to internal Air Force documents.