Gwynne Shotwell, the aerospace manufacturer's president, told journalists in Los Angeles an unmanned flight to the International Space Station in November would pave the way for a manned mission in April 2019.

"Predicting launch dates could make a liar out of the best of us. I hope I am not proven to be a liar on this one," she said.

NASA awarded contracts to SpaceX and Boeing in 2014 as part of its commercial crew program, aimed at helping private industry build spaceships to reach low-Earth orbit.

On August 3 the agency named the first nine astronauts who will fly to space on Boeing and SpaceX vehicles in 2019 -- a mix of novices and veterans.

Those named for the SpaceX test crew include shuttle veterans Bob Behnken, Michael Hopkins and Douglas Hurley, alongside naval aviator Victor Glover, a novice to spaceflight.

The flights to the ISS will be the first leaving US soil to put people into orbit since the iconic space shuttle program ended in 2011.

For seven years, NASA astronauts have hitched rides to the orbiting outpost on Russia's Soyuz spacecraft -- at a cost of some $80 million a seat.

A US government report released in July said it was unlikely that SpaceX would be able to send astronauts to the ISS next year.

Shotwell said however the mission would go ahead as soon as SpaceX was "ready to fly these folks safely."

"Next in line we want to make sure not only that we get these folks up and back safely but that that's reliable and a mission that we conclude," she added.

"We want to hit all the boxes do everything we need to do, to demonstrate that this vehicle is capable of taking astronauts up from US soil as often as NASA will allow us."

SpaceX unveiled its astronauts, all clad in blue overalls and smiling proudly in front of the module that will transport them to the ISS, to answer questions from the media.

"Being able to fly as a first flight a vehicle as a test pilot is a 'once in a generation' type of opportunity, so obviously I'm very thankful for it," said Hurley.

"But I would also say that we've got a lot of work left to do."