WASHINGTON -(Dow Jones)- Microsoft Chairman Bill Gates said Thursday he hoped the federal government would approve the use of spare communications airwaves quickly to help expand broadband Internet service to parts of the country where it isn't currently available.

He said if the use of radio spectrum that sits vacant between the spectrum used by television broadcasters to transmit their signals was allowed, it could lead to the rapid growth of Wifi Internet service.

"We're hopeful [white spaces spectrum] will be made available so that Wifi can explode," said Gates.

He said white spaces spectrum would help expand high-speed Internet access to rural areas of the country where commercial providers don't operate.

Speaking alongside of Gates, Microsoft's Chief Research and Strategy Officer Craig Mundie said the white spaces spectrum was the last chance to set aside airwaves to underpin the growth of Internet service in rural and underserved parts of the country.

"The white spaces [spectrum] is sort of our last hope to get some good spectrum," said Mundie. "The only way to do it is to use the unused tv channels and very smart radios."

The two were speaking at a breakfast meeting hosted by the Northern Virginia Technology Council, a trade group representing local technology firms.

Mundie said if the Federal Communications Commission didn't allow white spaces to be used for broadband service, the U.S. faced the prospect of falling behind the rest of the world competitively.

"Ultimately the public will pay the tab either because we fall behind as a society or we have to make extraordinary adjustments to catch up," he said.

Mundie said that Congress had the opportunity to allocate some spectrum for Wifi service when it was deciding what to do with the airwaves coming free from the shift by television broadcasters to a digital signal from their current analog one.

That switch over occurs next year.

Instead, Mundie said, Congress opted "to balance the budget a little bit by auctioning off that spectrum."

That auction selling the right to use the airwaves to commercial wireless companies is currently underway and has raised nearly $20 billion for the U.S. Treasury.

Mundie is assuming control for Microsoft's technology and policy development as Gates steps back from a day-to-day role with the company.

Gates is in Washington likely for the last time before he shifts the bulk of his time to running the charitable foundation he set up with his wife, Melinda Gates.

Microsoft has been in the vanguard advocating the use of white spaces spectrum to provide an alternative to existing broadband providers and to offer service in parts of the country where it isn't offered.

It, and other technology companies, argue the technology exists to support devices that use the spectrum lying in between the television channels and avoid any interference with those signals.

Mundie acknowledged that T.V. broadcasters and manufacturers of wireless microphones, which use the spectrum now, are opposed to the concept.

Several lawmakers on the House Commerce Committee and a majority of commissioners at the FCC have expressed their support for the use of white spaces spectrum, as long as the technology is sound.

FCC engineers are currently testing several prototype devices supplied by Microsoft, Motorola Inc. (MOT) and others to see if they can effectively detect potential interference.

The Microsoft device, which was the first to be tested in January, experienced shut down after overheating. This is the second time a prototype by the company has failed during testing. Last summer, during an initial phase of testing by the FCC, a device supplied by the company didn't work.

Microsoft has argued that in both cases, the problems were specific to those devices and nothing to do with the underlying technology.

"Microsoft continues to push for an unlicensed technology that simply does not work," said Dennis Wharton, executive vice president at the National Association of Broadcasters. "These interference-causing devices have failed multiple FCC tests, and by their own admission 'just stopped working.'"

A device supplied by Philips Electronics - a unit of the Netherlands' Koninklijke Philips Electronics N.V. (PHG) - was successful in the first round of tests last summer.