Boeing and SpaceX are preparing to begin the first manned test flights to the International Space Station (ISS) in 2017.

Last year, the companies secured contracts under Nasa’s commercial crew programme to fly astronauts on missions to the ISS.

Boeing’s fixed-price contract is valued at $4.2bn, while SpaceX’s is at $2.6bn.

SpaceX and Boeing will carry out a series of tests on their Dragon V2 and the CST-100 capsules respectively until 2017 prior to the flights to and from the station.

"If the manned flights to the ISS are successful, the US will be able to end its dependence on Russian spacecraft."

The Dragon V2 and the CST-100 capsules are designed to carry up to seven people to the space station.

Boeing Space Exploration vice president and general manager John Elbon said: "We’re on track, and it’s just as exciting as can be to be a part of it."

If the manned flights to the ISS are successful, the US will be able to end its dependence on Russian spacecraft.

Boeing plans to launch first crewed test flight in July 2017 with a Nasa astronaut and a Boeing test pilot onboard its CST-100.

Elbon was quoted by AFP as saying: "The first services mission then will begin in December of ’17."

SpaceX is working on its upgraded Dragon crew vehicle, which will take an unmanned test flight in 2016, a test flight with crew on board in early 2017.

Nasa administrator Charles Bolden said private companies are now able to reach low-Earth orbit supports the agency’s efforts to focus on sending humans to Mars by 2024, AFP reported.

Bolden said: "We made the conscious decision that if we are going to go to deep space, we need to turn over things that we are relatively sure we know how to do, access to low-Earth orbit, to American industry."