By Irene Klotz

Dec 12 (Reuters) - A commercial space company owned by Amazon founder Jeff Bezos has lost a challenge over NASA's plans to lease out one of the space shuttle's dormant launch pads in Florida, officials said on Thursday.

The company, Blue Origin, had filed a protest with the U.S. General Accountability Office, which arbitrates federal contract disputes. The GAO said in a decision it denied the company's protest.

Blue Origin is vying against another company owned by Elon Musk, co-founder of PayPal and chief executive of electric car company Tesla Motors, to lease Launch Pad 39A at the Kennedy Space Center.

Musk's company, Space Exploration Technologies, or SpaceX, already flies rockets from a leased launch pad at Cape Canaveral Air Force Station, just south of NASA's spaceport.

Blue Origin and SpaceX submitted proposals to NASA to take over maintenance and operations of Launch Pad 39A so it could be developed for commercial use.

Before NASA selected a winner, Blue Origin filed a protest, claiming its proposal to develop a multi-user facility better fit NASA's declared intention for the pad.

SpaceX, which launches its Falcon 9 rockets from nearby Cape Canaveral Air Force Station, wants to use the pad as a second Florida base.

Musk told Reuters after the protest was filed that he had no problem if other companies use the launch pad if SpaceX was awarded a five-year lease.

"I think it's kind of moot whether or not SpaceX gets exclusive or non-exclusive rights for the next five years. I don't see anyone else using that pad for the next five years," Musk told Reuters in September.

"I think it's a bit silly because Blue Origin hasn't even done a suborbital flight to space, let alone an orbital one. If one were to extrapolate their progress, they might reach orbit in five years, but that seems unlikely," he said.

Blue Origin contended the NASA solicitation "provided for a preference in favor of a multi-user (as opposed to an exclusive use) approach to utilizing the launch pad," the GAO said in its ruling on Thursday.

"NASA took the position that neither approach was favored," the ruling said.

"GAO agreed with NASA, and in its decision concluded that there was no preference for either approach," the GAO added.

NASA had hoped to turn over pad operations to a commercial user by Oct. 1, 2013. The delay is costing NASA about $100,000 per month, agency officials said.

SpaceX said it had no comment on the GAO ruling. Blue Origin officials did not immediately reply to a request for comment.