(Reuters) - An attorney for a group of 13 state attorneys general who filed a lawsuit in hopes of stopping T-Mobile U.S. Inc's $26 billion merger with Sprint Corp has requested a new trial date for the case.

In a letter to Magistrate Judge Robert Lehrburger dated July 31, attorney Glenn Pomerantz said the states are requesting a new trial-ready date of Dec. 9 or as soon after that date that the court can schedule the trial, adding that the Oct. 7 trial date proposed earlier is "unworkable."

The states said they are still awaiting documents from the companies and it may take until late next month until they receive them. The companies "now unfairly seek to sandbag (the suing) states by forcing them to go to trial in just two months on a new transaction they have not had an opportunity to fully examine."

Judge Lehrburger has set a hearing for Thursday on the case in New York.

Sprint and T-Mobile did not immediately comment late on Wednesday.

Last week, the U.S. Justice Department approved the tie-up, clearing a major hurdle to a deal that would merge the United States' third and fourth largest wireless carriers. The companies have agreed to divest Sprint's prepaid businesses including Boost Mobile to Dish Network Corp in order to move ahead with the merger.

(Reporting by David Shepardson in Washington and Kanishka Singh in Bengaluru; Editing by Sandra Maler)