Sprint Corporation, the country's third largest mobile phone company, is buying US Unwired Inc. for 1.3 billion dollars, Sprint said Monday. With the purchase, Sprint is buying the cooperation of US Unwired, which filed a challenge last month against to the Sprint-Nextel deal. The two companies said that Monday's agreement would end the litigation, Bloomberg financial news service reported. The Nextel acquisition will give more muscle to Sprint in facing off the two U.S. giants Cingular Wireless LLC and Verizon Wireless. A series of mergers in the mobile phone branch has taken place in recent months. US Unwired holders will receive $6.25 a share in cash, Sprint said. The Louisiana-based company has about 500,000 customers. --SP 2230 Local Time 1930 GMT