XM ( XMSR) and Sirius ( SIRI) climbed Wednesday on speculation that U.S. regulators are very close to granting approval to the merger of the two satellite radio broadcasters.

According to a headline on Briefing.com, the buzz suggested that the Justice Department and the Federal Communications Commission could have a decision tonight. The Web site didn't list any sources for the rumor.

Some merger watchers remain skeptical.

"We do not anticipate a decision tonight or in the immediate future," says David Trout of M&A Researcher. Trout was among the first deal watchers to point out that the regulators were in no hurry to start the needed merger review last year.

The proposed $4.6 billion deal is awaiting regulatory approval from antitrust lawyers at the Justice Department, as well as from consumer advocates at the Federal Communications Commission.

Observers say the highest hurdle for approval is convincing antitrust officials that satellite radio faces formidable competition from conventional radio and new devices like Apple's iPod.

Company representatives declined to comment on the speculation.

Sirius shares were adding 13 cents to $2.78 and XM was up 41 cents to $11, bucking a selloff in the tech sector Wednesday.

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