The launch of the company's Falcon 9 rocket and Dragon capsule from Cape Canaveral Air Force Station has not yet been rescheduled.

"We believe that there are a few areas that will benefit from additional work," said Kirstin Brost Grantham, a spokeswoman for the company, also known as SpaceX.

"We will continue to test and review data. We will launch when the vehicle is ready," she said.

The flight will be the second and possibly last test flight before privately owned SpaceX begins delivering cargo to the station under a $1.6 billion NASA contract.

The firm, based in Hawthorne, California, and founded by Internet entrepreneur Elon Musk, hopes to combine its two remaining test flights into one with a berthing at the space station, pending NASA's approval.

SpaceX successfully launched, orbited and landed a Dragon capsule during a test flight in December 2010.

NASA has hired SpaceX, as well as a second company, Orbital Sciences Corp to fly supplies to station after the retirement of the space shuttles last year.

The station, a $100 billion research laboratory flying about 240 miles above Earth, also is serviced by Russian, European and Japanese ships.

SpaceX and Orbital, which plans to debut its Antares rocket and Cygnus cargo capsule this year, are in line to be the first commercial firms to fly to the outpost, which is staffed by rotating crews of six astronauts.

SpaceX also has a $75 million NASA contract to upgrade its Dragon capsule to carry astronauts.

The United States hopes to break Russia's monopoly on crew transportation to the station by supporting private industry efforts to develop passenger spaceships. Congress allotted $406 million for NASA's so-called Commercial Crew program for the year that began October 1.

Russia charges NASA about $60 million per person for rides to the station.

Also this week, United Launch Alliance, a partnership of Boeing and Lockheed Martin, has hired NASA's former shuttle launch director Michael Leinbach to oversee the company's transition from launching U.S. government satellites to launching people.

Of the four firms NASA currently is backing for space taxi development, all but SpaceX plan to use United Launch Alliance's Atlas 5 rockets to put their spaceships into orbit.

"Mike's expertise in human launch systems provides a strong synergy in bringing together two world-class launch cultures," Jerry Jamison, a United Launch Alliance vice president, said in a statement.

NASA intends to release a solicitation for the next phase of its Commercial Crew program in February.

Other firms currently receiving NASA funding for space taxi development are Boeing, Sierra Nevada Corp, and Blue Origin, a startup owned by Amazon founder Jeff Bezos.

(Editing by Kevin Gray and Eric Walsh)

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