SoftBank Group Corp., which is struggling to turn around its U.S. wireless carrier Sprint Corp., posted an 88 percent drop in third quarter profit.

Net income fell to ¥2.3 billion ($20 million) in the three months ended Dec. 31, from ¥18.7 billion a year earlier, the company reported Wednesday. Sprint shares this week are trading at less than half their price when SoftBank spent $22 billion for a controlling stake in 2013.

SoftBank stock has been hammered by mounting pessimism about billionaire Chairman Masayoshi Son's efforts to turn around Sprint even as its Japanese wireless business continues to grow. With about $100 billion of debt, ending losses in the U.S. is seen as critical to reviving SoftBank's share price.

"Domestic operations still offer stable earnings, but that business can't be expected to grow much," Tomoaki Kawasaki, an analyst at Iwai Cosmo Securities Co., said before the earnings announcement. "Sprint seems to have hit the bottom, but the recovery is slow and will take a while, as Son himself has acknowledged."

Operating profit for the quarter was ¥189.6 billion. The company did not provide full-year forecasts.