President Donald Trump used a term from US segregationist history to describe the relationship between the Air Force and his newest military branch, the Space Force, calling it "separate but equal."

"We must have American dominance in space. Very importantly, I'm hereby directing the Department of Defense and Pentagon to immediately begin the process necessary to establish the Space Force as the sixth branch of the armed forces. That's a big step," he said in the White House East Room during a meeting of his National Space Council Monday.

"We are going to have the Air Force and we are going to have the Space Force: separate but equal, it is going to be something so important," he said.

The term "separate but equal" became a legal precedent following an 1896 Supreme Court ruling Plessy v. Ferguson that said the use of racially separate facilities, if equal, was not discrimination. That legal rationale was deemed unconstitutional through a series of Supreme Court decisions, ending with 1954's Brown v. Board of Education.

In addition to calling for the Space Force, Trump signed Space Policy Directive-3 Monday, part of his administration's push to lead in the field of space.

Trump previously floated the idea of adding a "Space Force" branch to the US military — a concept that has received some support on Capitol Hill but drawn skepticism from the Pentagon.

Space Policy Directive-3 is primarily focused on satellite traffic management and mitigating debris in space. The policy, executive secretary of the National Space Council Scott Pace told reporters, "seeks to address the challenges of a congested space environment."

"If we're going to expand the economy in space, we need to make sure it's done in a sustainable way," Pace said.

For the private sector's space activity, the primary effect of the policy is "more rapid and more accurate information on where they can launch," as well as "flexibility in launch windows," and satellites having "more time to put toward revenue-generating activities rather than maneuvering" to avoid collision risks, Pace said.