The interminably long merger approval process between XM (Nasdaq: XMSR) and Sirius (Nasdaq: SIRI) is about to get even longer.

With the FCC unlikely to nod along with last week's Justice Department approval by the end of today, the proposed pairing of the satellite radio upstarts will drag into its sixth quarter of limbo tomorrow.

"I'm not sure we'll make it by the end of the first quarter any longer," FCC Chairman Kevin Martin said two weeks ago. "I've got the staff drafting various options. I haven't figured out what I think we should do on it yet."

Even though the comments were made just before the Department of Justice gave the deal its blessing -- and the FCC has been portrayed as more merger-friendly than its regulatory peer -- it's probably not fair to hold Martin to his initial first-quarter deadline when it took the DoJ more than 13 months to get out of the way of the satellite-radio lovebirds.

Still, the final ruling should be days -- not weeks or months -- away. It would be a shock to see the FCC block the deal.

Last week, I covered both the challenges and opportunities that await XM and Sirius after their union is complete. These are clearly interesting times for the combined operator that will watch over 17.3 million of radio's biggest fans.

It may also prove to be just as interesting for the regulatory bodies that yea or nay the deals that come down the pike. Why did Google (Nasdaq: GOOG) have to wait so long to consummate its deal with DoubleClick while Microsoft (Nasdaq: MSFT) was able, in the blink of an eye, to hook up with aQuantive in a deal valued at nearly twice as much? If the argument is that Google is a global dominator in online advertising, then why did the XM-Sirius deal take so long when Clear Channel (NYSE: CCU) is a larger radio broadcaster than XM and Sirius combined?

The regulatory approval process should never be rushed, but it's taking way too long to come up with the obvious solutions.

Here are some other recent XM stories on its long courtship with Sirius:

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Longtime Fool contributor Rick Munarriz is such a big satellite-radio fan that he subscribes to both XM and Sirius. He does not own shares in any of the companies in this story. He is also a member of the Rule Breakers analytical team, seeking out the next great growth stock early in its defiance. The Fool has a disclosure policy.