Representatives Mike D. Rogers, Republican of Alabama, and Jim Cooper, Democrat of Tennessee, have pressed hard for the idea in Congress. They argue that a new military branch is needed because the Air Force does not pay enough attention to outer space. What’s more, they say, Russia and China are developing anti-satellite weapons that could imperil American satellites.

“We could be deaf, dumb and blind within seconds,” Mr. Cooper, who sits on the House Armed Services Committee with Mr. Rogers, said in February at a space forum at the Center for Strategic and International Studies. “Seldom has a great nation been so vulnerable.”

On Thursday, Mr. Rogers sounded a similar theme. A bill he and Mr. Cooper backed last year would have created a space corps under the umbrella of the Air Force. But the president took the idea a step further when he said he wanted a space force that would be “separate but equal,” an eyebrow-raising description that would essentially create a military service to join the Army, Navy, Air Force, Marines and Coast Guard.