Kohl also questioned if Sprint Nextel could remain in business if the deal is approved.

Three Democratic members of the House of Representatives, John Conyers Jr. of Michigan, Ed Markey of Massachusetts and Anna Eshoo of California, also wrote a letter to the DOJ and the FCC Wednesday, calling on the agencies to carefully review the deal.

"We believe that AT&T's acquisition of T-Mobile would be a troubling backward step in federal public policy -- a retrenchment from nearly two decades of promoting competition and open markets to acceptance of a duopoly in the wireless marketplace," they wrote.

The IDG News Service