US President Donald Trump has signed Space Policy Directive 4 to facilitate the creation of a space force as a sixth branch of the country’s military.

The new branch will be included within the Department of the Air Force, comparable to the establishment of the US Marine Corps under the remit of the US Navy.

During his speech at the White House signing ceremony Trump said: “We are investing in new space capabilities to project military power and safeguard our nation’s interests, especially when it comes to safety and defence.

“This directive calls on the secretary of defence to develop a legislative proposal that will establish the structure and authority of the space force as the sixth branch of the US Armed Forces. That would mean that the highest ranking person there would go onto the Joint Chiefs of Staff.”

The directive mandates the Department of Defense to develop a legislative proposal for the formation of a US space force to deter and counter threats in space.

Although the president said the new branch would be established by 2020, Space Policy Directive 4 will first require approval from Congress that includes a Democrat-controlled House of Representatives.

“I think we will have great support from Congress because they do support something when we are talking about [something of] such importance,” said Trump.

"My administration has recognised space as a warfighting domain and made the creation of the space force a national security priority."

“And a lot of the generals, a lot of the people involved, have been speaking to Congress with some very interesting dialogue going on.”

Under Space Policy Directive 4, the role of the US space force will be to organise, train, and equip military space forces of the nation to operate in space and to perform offensive and defensive space operations, and joint operations in all domains.

One of the key priorities of the proposed space force includes protecting the interests of the US and its allies from hostile acts in and from space.

Trump added: “America must be fully equipped to defend our vital interests. Our adversaries’ training forces are developing technology to undermine our security in space and they’re working very hard at that. That’s why my administration has recognised space as a warfighting domain and made the creation of the space force a national security priority.

“The space force will organise, equip and train the next generation of warriors to deter aggression and defend the nation, our allies, and American interests, against hostile actions in the form of space and taking place in space.”

In January, Trump delivered the Missile Defense Review to the Pentagon, which included provisions for creating a missile defence system in space to defend against threats from nations, such as Iran and North Korea.

–Additional reporting by Talal Husseini.