Private equity buyout firm Japan Industrial Partners has submitted a $15 billion bid to acquire Toshiba Corp, without having secured the backing of banks raising doubts over the viability of the proposed deal, according to a report by Reuters.

JIP’s proposal includes a commitment of almost half of the $15 million from a consortium of over ten investors including utility company Chubu Electric Power Co Inc and financial services group Orix Corp.

The report cites information from Japan’s Nikkei newspaper as revealing that JIP’s proposal appears not to have included commitment letters from banks, with the fund aiming to pull together financing by the end of this month if Toshiba accepts the offer from its preferred bidder.

Read more: Private Equity Wire