WASHINGTON — Vice President Mike Pence promoted a proposed Space Command on Thursday as “an idea whose time has come” in comments at the Pentagon to unveil a few more details about President Trump’s plan to create another military force, this one for outer space, and for it to be in operation by 2020.

Mr. Trump’s space dreams still have to go through a divided Congress to come true, but initially reluctant Pentagon officials have lined up behind the proposal and now say that they will do what they can to bring it to fruition.

“The time has come to write the next great chapter in the history of our armed forces, to prepare for the next battlefield where America’s best and bravest will be called to deter and defeat a new generation of threats to our people, to our nation,” Mr. Pence told an audience at the Pentagon. He called for Congress to allocate an additional $8 billion for space security systems over the next five years.

Mr. Trump, for his part, posted on Twitter on Thursday: “Space Force all the way!”

But that may be a tall order. The administration cannot just create a Space Force on its own; it has to go through Congress, where critics abound.