Sprint Corp. (S - Get Report) and T-Mobile U.S. Inc.'s (TMUS - Get Report) $26 billion merger could close as soon as the first quarter next year, T-Mobile CFO J. Braxton Carter told the Morgan Stanley TMT Conference in Barcelona, according to Reuters. 

The deal, which would combine the third and fourth largest mobile carriers in the country, was first agreed upon in April. 

"The only remaining thing that is happening is depositions with the DoJ, which have started and will be completed in a few weeks," Carter told the conference, according to Reuters. "At this point, it's more pointing to the second quarter as more probable (but) it could still be first quarter."

The merger could face regulatory challenges on antitrust grounds, but Carter said that the two companies have provided 25 million pages worth of documents to the Department of Justice and has filed 600 pages of public information statements with the Federal Communication Commission, according to Carter.