What will the Space Force actually do?

It is not intended to put troops into orbit, but will protect US assets - such as the hundreds of satellites used for communication and surveillance.

It comes as US military chiefs see China and Russia making advancements in the military final frontier.

Vice-President Mike Pence previously said the two nations had airborne lasers and anti-satellite missiles that the US needed to counter.

"The space environment has fundamentally changed in the last generation," he said. "What was once peaceful and uncontested is now crowded and adversarial."

Space Force will build on the work of the existing US Space Command (SpaceCom), which was created in August to handle the US military's space operations.

Air Force Secretary Barbara Barrett said the Space Force would comprise around 16,000 Air Force and civilian personnel.

It will be led by Air Force General Jay Raymond, who currently runs SpaceCom.

Earlier this month, Russia's President Vladimir Putin suggested US expansion in space posed a threat to Russian interests, and required a response from Russia.

"The US military-political leadership openly considers space as a military theatre and plans to conduct operations there," Mr Putin said. (BBC)