AT&T is in the process of buying T-Mobile USA from Deutsche Telekom for about US$39 billion, and the companies should expect some headaches before the deal is completed, according to an unnamed Federal Communications Commission official. The cell service providers are expecting to finish the sale within about 12 months.

FCC: AT&T / T-Mobile deal won’t come easy

The FCC hasn’t begun its formal evaluation of the planned purchase to determine whether or not the deal is in the public interest. “There’s no way the chairman’s office rubber-stamps this transaction,” the anonymous FCC official told the Wall Street Journal. “It will be a steep climb to say the least.”

AT&T announced earlier this week that it struck a deal with Deutsche Telekom to buy T-Mobile USA. The deal includes all of T-Mobile’s customers along with the carrier’s wireless spectrum. “At closing, AT&T will immediately gain cell sites equivalent to what would have taken on average five years to build without the transaction, and double that in some markets,” AT&T said in a statement.

The deal will also make AT&T the single largest mobile service provider in the U.S. Verizon, currently the country’s largest mobile provider, says it doesn’t have any interest in trying to block the deal.