SpaceX has postponed by a week its bid to become the first private company to attempt to launch an unmanned cargo vessel to the International Space Station.

"After reviewing our recent progress, it was clear that we needed more time to finish hardware-in-the-loop testing and properly review and follow up on all data," SpaceX spokeswoman Kirstin Brost Grantham said late Monday.

"While it is still possible that we could launch on May 3rd, it would be wise to add a few more days of margin in case things take longer than expected.

"As a result, our launch is likely to be pushed back by one week, pending coordination with NASA," she said in a statement, adding that the company would announce the new target date once it was determined.

SpaceX CEO Elon Musk announced the decision via Twitter, writing: "Am pushing launch back approx a week to do more testing on Dragon docking code. New date pending coordination with NASA."

Last Monday NASA said there was a good chance SpaceX would soon become the first private company to attempt to launch its spacecraft to the ISS on an unmanned cargo flight.

SpaceX aims to carry out a fly-by of the ISS and a berthing operation in which the reusable spacecraft, the Dragon, will approach the ISS as the crew aboard the orbiting outpost uses a robotic arm to dock it.

The gumdrop-shaped Dragon capsule will carry 521 kilograms (1,148 pounds) of cargo for the space lab and will also aim to return a 660 kg (1,455 lb) load to Earth, Michael Suffredini, ISS program manager, said last week.

SpaceX -- owned by Internet entrepreneur and PayPal co-founder Musk -- made history with its Dragon launch in December 2010, becoming the first commercial outfit to send a spacecraft into orbit and back.

SpaceX and several other companies are competing to be the first to operate a private capsule that could tote astronauts and cargo to the ISS, after NASA retired its shuttle program last year.

Russia's Soyuz capsule is currently the world's sole means of transporting astronauts and cargo to the orbiting space station.

Other companies in the private space race include aerospace giant Boeing, the Nevada-based Sierra Nevada Corporation, and Washington state-based BlueOrigin LLC.

NASA has channeled $270 million to firms hoping to join the new commercial space race and hopes to foster a billion-dollar industry over the next decade.

In a draft budget submitted to Congress in February, President Barack Obama requested $829 million to develop commercial flights to the ISS, partly to end US reliance on Russian craft to deliver astronauts and re-supply the station.

The privatization of space transport is expected to pave the way for tourism, with British tycoon Richard Branson's Virgin Galactic offering $200,000 reservations for journeys into space.

The company has already taken in $60 million in sales and deposits, with more than 500 individuals -- including Hollywood stars and other multi-millionaires -- adding their names to the list.

The prices of the only trips into space so far, which were sold to private individuals traveling on Russian spacecraft, have ranged from $45 million to as much as $150 million.