A first of its kind demonstration flight by SpaceX's Dragon capsule on Thursday successfully completed a key milestone in its mission - a fly-under of the International Space Station, NASA said.
The privately owned spacecraft "passed directly below the ISS at a distance of 2.5 kilometres, fulfilling all demonstration objectives for the day," the US space agency announced on the microblogging site Twitter.
"The SpaceX Dragon capsule fly-under of the ISS has been successfully completed," it added. More details are expected during a 10am (4pm SAST) news conference.
The next step is for the spacecraft to berth with the orbiting lab, in order to unload the half ton of supplies it has brought to space and then get restocked with gear to return to Earth.
NASA said it would meet at 9pm (3am SAST Friday) to decide whether to give the go-ahead for the spacecraft to attempt its approach to the $100-billion research outpost.
Astronauts aboard the ISS are planning to help the operation by reaching out with the station's robotic arm, built by the Canadian space agency, to grab the spacecraft so it can latch on to the Harmony module of the station.
If NASA gives the go ahead, the robotic arm grab attempt would begin at 8.06am (2.06pm SAST) with the docking itself scheduled for 11.05am (5.05pm SAST), a NASA spokesperson said.
Carrying cargo but no humans yet, SpaceX's Dragon capsule launched on Tuesday atop the company's Falcon 9 rocket, marking the first time a commercial enterprise has sent its own craft to the orbiting lab.
Currently, only the space agencies of Europe, Russia and Japan can send supply ships to the ISS. The United States lost that ability when it retired the space shuttle fleet last year.
California-based SpaceX, owned by internet entrepreneur and billionaire Elon Musk, hopes that its gumdrop-shaped Dragon capsule will be able to carry astronauts to the ISS in about three years' time.
SpaceX and a handful of other companies are being helped in their endeavours with seed money from NASA to build cargo and crew capability.
SpaceX has a $1.6-billion contract with NASA to supply the ISS with cargo in the coming years. Orbital Sciences has a $1.9-billion contract and is scheduled for its first launch attempt later this year.