Billionaire Masayoshi Son’s SoftBank Group said it would sell a $14bn chunk of its Japanese mobile unit, adding to a string of asset sales aimed at bolstering the company’s debt-laden balance sheet.

The sale will lower its stake in the telecom unit, known as SoftBank to 40% from 62%, ending its position as majority shareholder. It will remain the largest shareholder of the company, which is one of Japan’s biggest mobile-phone providers.