President Donald Trump’s administration will call on Congress to allocate $8 billion over the next five years to establish the U.S. Space Force as the sixth branch of the military, Vice President Mike Pence said.

“It’s not enough to have an American presence in space,” Pence said Thursday in a speech at the Pentagon. “We must have American dominance in space. And so we will.”

Trump first broached the idea in March, reviving a debate that began almost 20 years ago about whether the Pentagon’s space activities should be moved to a new command. In June, Trump called for the new branch to be created, despite resistance from the Air Force, which currently oversees military space programs. It wasn’t immediately clear whether the new force would be a component of the Air Force, as the Marine Corps is to the Navy.

Secretary of Defense James Mattis had also disapproved of the idea in the past, saying last year he opposed creating additional bureaucracy at the Pentagon.

On Thursday, Mattis said “space is one of our vital national interests” and is “no longer a new domain.”

Congress would have to approve a new military service, and lawmakers have been divided on the idea. The new branch would need to compete for money with other big, politically protected Defense Department priorities that Congress already funds.

Read More: What’s a Space Force, and Can Trump Really Start One?: QuickTake

The U.S. already has a space-based military footprint. The sky is teeming with spy satellites and other platforms that support government surveillance, communications, weather forecasting and other activities. The Air Force also has a top-secret aircraft, the X-37B, built by Boeing Co., which orbits the earth for extended periods.

Much of the push to formalize an off-planet branch of the U.S. armed forces is motivated by space investment by Russia and China. In 2007, China fired a missile to destroy an aged weather satellite, demonstrating in a dramatic fashion its ability to deploy anti-satellite weapons.

Even before Trump’s comments, the Defense Department was under orders to formulate a “concept of operations” document for space war fighting.