Softbank Corp. President Masayoshi Son lashed out at fellow billionaire Charlie Ergen, saying he doesn't have the expertise to run Sprint Nextel Corp., the U.S. mobile phone company both men are trying to take over.

Ergen, the chairman of Dish Network Corp., doesn't have a wireless background, making him a poor fit to run Sprint, Son said Tuesday at an event in Tokyo. He questioned the wisdom of Ergen's strategy to combine Sprint with a satellite TV company instead of another mobile phone carrier like his own.

"I just deliver the results, instead of big-mouthing about the future," Son said. "Do you want to attach a satellite dish to your smartphone? It's going to become much heavier. I don't see any real meaningful value that he can offer to the smartphone customers."