Japan's three biggest banks have started talks with Softbank Corp. on extending loans of up to ¥1.5 trillion to fund the company's planned acquisition of Sprint Nextel Corp., the third-largest U.S. telecom carrier, according to banking sources.

Softbank is also considering buying MetroPCS Communications Inc., the fifth-biggest mobile company in the United States, as well as Washington-based Clearwire Corp., a wireless broadband services provider.

Mizuho Corporate Bank, Bank of Tokyo-Mitsubishi UFJ and Sumitomo Mitsui Banking Corp. intend to support Softbank's apparent attempt to expand overseas on the back of the strong yen, the sources said Friday.