In June, President Donald Trump ordered the creation of Space Force, arguing the Pentagon needs it to tackle vulnerabilities in space and assert US dominance in orbit.

The creation of Space Force is not a done deal, as it first needs to be approved by Congress., and it has met with some skepticism from lawmakers and defense officials who are wary of the cost and added bureaucracy.

But Pence was unequivocal in presenting the administration's wish for it to become a reality -- preferably by 2020, the end of Trump's term in office.

"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," Pence told an audience at the Pentagon.

"The time has come to establish the United States Space Force."

Shortly after Pence's speech, Trump tweeted: "Space Force all the way!"

The Pentagon's existing military branches are: the Navy, Coast Guard, Marine Corps, Army and Air Force.

Given the stakes about building a new branch of the military, the issue is likely to be a political football.

Currently, the Air Force oversees most space capabilities and there is some push back from officials who worry Space Force's mission would be duplicative and create turf wars.

But Pence said an independent Space Force was essential to counter Russia and China, which are "aggressively" working toward anti-satellite capabilities.

"China and Russia have been conducting highly sophisticated on-orbit activities that could enable them to maneuver their satellites into close proximity of ours, posing unprecedented new dangers to our space systems," he said.

The White House said in a statement that "President Trump knows that space is integral to our American way of life and economic prosperity, and is a vital domain for national defense."

- US Space Command -

Pence outlined a series of steps the Pentagon will undertake ahead of the creation of Space Force.

Key among these is the creation of US Space Command, a new organizational body that would draw in members of existing military branches.

The vast US military divides the globe into various commands, such as Central Command in the Middle East or Indo-Pacific Command in Asia, and so a new Space Command would be on an equal footing with these.

It would require a new headquarters and major organizational changes.

Defense Secretary Jim Mattis said this week that Pence is Trump's "point man" for Space Force, and Pentagon officials are working closely with his office.

But just last year, Mattis voiced skepticism on the need to create a separate Space Force.

In a letter to a US congressman, he said he did "not wish to add a separate service that would likely present a narrower and even parochial approach to space operations," adding it would create extra bureaucracy and cost.

On Tuesday, however, the Pentagon chief said he fully supported the idea of creating a new US Space Command.

"We need to address space as a developing, war-fighting domain and a combatant command is certainly one thing that we can establish," he said.

The Pentagon sent a report to Congress on Tuesday detailing steps towards meeting Trump's order.