"Requests from the FCC staff for additional information are to be expected given the detailed review they are undertaking," AT&T spokesman Michael Balmoris said.
"In this case, the FCC is seeking supplemental information on our commitment, following merger approval, to bring 4G LTE mobile broadband to 97 per cent of all Americans," Balmoris said.
Earlier this month, AT&T sent a letter to the FCC about the merger that accidentally included confidential data that has since been removed, according to a story in the Wall Street Journal.
The Journal said that the document had said AT&T had considered and rejected plans to expand its network on its own to 97 per cent of the U.S. at a cost of $3.8 billion, which is roughly one-tenth of the price tag for its proposed purchase of T-Mobile USA.
But a source familiar with the matter told Reuters that this information was theoretical.
"All the money in the world isn't going to deal with it in time because of spectrum exhaustion," the person said.