A private spaceship is close to heading to the International Space Station as SpaceX's Dragon capsule and Falcon 9 rocket have been joined, the company says.

The cargo capsule and the launch vehicle have been assembled at Cape Canaveral in Florida, SpaceX Chief Executive Officer Elon Musk reported in a tweet.

The launch, probably in late April, will be an unmanned mission to test the Dragon capsule's ability to rendezvous and dock with the space station, Newscientist.com reported Tuesday.

The space drone is expected to carry some nonessential "demonstration cargo" that will be transferred to the space station and will be loaded with station cargo for return to Earth.

Following last year's retirement of NASA's space shuttles, the main means of ferrying supplies to the orbital outpost has been Russian Progress cargo ships.

If the upcoming SpaceX launch is successful, Dragon would be the first commercial craft to attempt to visit the International Space Station.