Washington — Vice President Mike Pence announced Thursday that the Pentagon has begun planning to create a Space Force, embarking on an effort to create the first new armed service since 1947.

In June, President Donald Trump called for the establishment of the sixth armed service, to join the Air Force, Army, Marine Corps, Navy and Coast Guard. Thursday's plan, which requires authorization and funding from Congress, would develop forces to defend satellites from attack and other space-related tasks. China and Russia are the nation's primary rivals in space.

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

The force would be created by 2020, Pence said. Before that, the Pentagon will create the U.S. Space Command, which will be led by a four-star officer and draw forces from the other armed services.

When the proposal for a separate force was launched last year, Defense Secretary Jim Mattis resisted it. He wrote to Congress that it would “likely present a narrower and even parochial approach to space operations.”

But Mattis signaled earlier this week that establishing a combatant command was a possibility.

"We need to address space as a developing war fighting domain and a combatant command is certainly one thing that we can — we can establish," Mattis told reporters. "This is a process we're in. We are in complete alignment with the president's concern about protecting our assets in space that contribute to our security, to our economy. And we're going to have to address it as other countries show a capability to attack those assets."

The Pentagon's plan, released Thursday, identifies China and Russia as "strategic competitors" that are "explicitly pursuing space war fighting capabilities to neutralize U.S space capabilities in a time of conflict." For example, Russia and China are pursuing anti-satellite weapons, including lasers, to "reduce U.S. military effectiveness."

Pence said the White House already has been working with Congress to develop the plan. Next year's budget will seek funding and authorization for the venture.

“We’re building bipartisan support for our plan," Pence said.

The top House Republican and Democrat on an Armed Services Committee panel on strategic forces applauded the plan. Rep. Mike Rogers, an Alabama Republican, and Jim Cooper, a Democrat from Tennessee, said in a joint statement that they had been warning for years about the need to beef up military capabilities in space.

"This report is a step in a multi-year process that we think will result in a safer, stronger America," the statement reads.

The Air Force, the newest of the armed services dating to 1947, has the largest stake in space. It already contains a Space Command, which it established in 1982. The new force would likely be carved out a chunk of the Air Force, creating two smaller, weaker services, according to military analysts.

"This is a half-baked idea," said Loren Thompson, a defense industry consultant and military analyst at the Lexington Institute. "It will disrupt existing military relationships and add nothing of value. Nobody in the Pentagon believes creating a Space Force makes sense. If that same view prevails in Congress, then it isn't going to happen."

A better idea would be elevating an organization within the Air Force to deal with space, Thompson said.

"Creating a separate service will just add to dysfunction at the Defense Department," he said.

Pence identified interim steps to creation of the Space Force in two years. They include the new command and creating a civilian position as an assistant Secretary of Defense for Space to oversee the transition.

“The space force is the next and natural evolution of American military strength," Pence said.