NEW YORK ( TheStreet) -- U.S. Cellular ( USM) has announced a $480 million deal to sell its Chicago, St. Louis, central Illinois and three other Midwest markets to subsidiaries of Sprint Nextel ( S). The sale encompasses PCS spectrum and around 585,000 customers, according to a statement released by U.S. Cellular on Wednesday. The Chicago-based firm says the deal lets it focus on markets where the company has a strong position and will also boost efficiency. "Exiting these markets enables us to play to our strengths in markets where we have higher penetration and where we can effectively sharpen our proven strategy to differentiate the U.S. Cellular customer experience from other wireless carriers," said Mary Dillon, the U.S. Cellular CEO, in the company's statement. As part of the deal, around 10% of the U.S. Cellular customer base will move to Sprint. The transaction, which is expected to close in mid-2013, continues the trend of telecom sector consolidation. Last month, for example, Japanese firm Softbank reached a $20.1 billion deal to acquire a 70% stake in Sprint. The huge injection of capital is seen as bolstering Sprint's arsenal in the telecom battle against AT&T ( T) and Verizon ( VZ). Sprint shares dipped 1.2% to $5.66 before the market open on Wednesday. --Written by James Rogers in New York. Follow @jamesjrogers >To submit a news tip, send an email to: firstname.lastname@example.org.