Almost two years to date since AT&T pulled its bid for T-Mobile USA, rival carrier Sprint is reportedly preparing its own offer to purchase the fourth largest carrier in the US. Sprint is currently looking into regulatory concerns that could be voiced if the third largest US carrier acquired the company which runs the fourth largest US carrier.

Sprint Corp. S +3.44% is working toward a possible bid for rival T-Mobile US Inc.,TMUS +8.65% people familiar with the matter said, setting the stage for a giant telecom merger that if permitted by regulators would leave the U.S. wireless market dominated by three big companies.