Overland Park ? Sprint Corp.’s main affiliate, AirGate PCS Inc., said Monday it had filed suit against Sprint, the sixth affiliate to challenge the company’s pending acquisition of Nextel Communications Inc.

AirGate, owned by Lubbock, Texas-based Alamosa Holdings Inc., said the merger could allow Sprint to violate its exclusivity agreements by selling Nextel products in AirGate’s territories.

Five other affiliates have made similar claims, asking courts across the country to stop the consolidation. Federal regulators approved the acquisition last week.

The company is negotiating with Alamosa but doesn’t believe the lawsuit will hold up the merger, Sprint spokesman Scott Stoffel said Monday.

Sprint agreed last month to buy one of the affiliates, U.S. Unwired, for $1.3 billion. Sprint has reached agreements with two affiliates, iPCS Wireless Inc. and UbiquiTel Inc., that ended their lawsuits.

Sprint remains in discussions with two more affiliates, Enterprise PCS and Gulf Coast Wireless.

AirGate, which serves 1.4 million subscribers in 19 states, asks in its lawsuit for a court injunction preventing Sprint from changing the status quo.

AirGate said it was in negotiations with Sprint on its concerns but filed the suit in case it couldn’t complete negotiations before the merger is completed.

Sprint shares lost 54 cents Monday to $26.04 on the New York Stock Exchange. The stock has traded in a 52-week range of $17.80 to $27.08. Alamosa shares lost 38 cents to $15.45 on the Nasdaq stock exchange, near the high end of its 52-week range of $6.73 to $16.25.