US private equity firms Cerberus Partners and Providence Equity Partners are reportedly preparing a bid for Vodafone Group's Japanese mobile subsidiary, which could value the business at $15bn (€12.4bn).

The Wall Street Journal reports today that the pair are near to securing financing for an offer, which would pit them against a €11.6bn ($14bn) bid already on the table from Japanese internet conglomerate Softbank. The newspaper cites sources familiar with the matter.