WASHINGTON — When the Federal Communications Commission auctioned off two exclusive licenses to create the satellite radio industry 10 years ago, it did not mince words on whether the competing providers could merge.

The agency said that one licensee will "not be permitted to acquire control" of the other.

But never say never.

"The FCC can undo anything it does," said Andrew Schwartzman, CEO of the Media Access Project, a public-interest law firm in Washington.

On Monday, Washington, D.C.-based XM Satellite Radio Holdings Inc. and New York City-based Sirius Satellite Radio Inc. announced a deal valued at $4.84 billion at the close of Wall Street trading yesterday.

The companies will need approval from the Justice Department as well as the FCC. The Justice Department typically goes first in satellite mergers. If it blocks the deal, it's game over. But Schwartzman said that is unlikely to happen.

"My guess is this Justice Department will be willing to accept any plausible argument that is presented to it," he said. "The FCC is a much tougher case."

The Justice Department looks at how mergers affect competition. The companies will argue that since the industry was created in 1997, the market has changed. It's no longer radio, it's "audio entertainment," which includes terrestrial radio, digital high-definition radio that offers more stations, Internet stations and even iPods.

The FCC requires that any transfers of control of licenses to use public airwaves be done only if it serves the "public interest, convenience and necessity."

The companies' argument to the FCC, previewed Monday, will be that a combined satellite provider will offer more program choices for listeners.