A Japanese investment fund has secured about ¥1 trillion ($6.8 billion) to buy out Toshiba and has notified the embattled conglomerate that the amount was offered by a group of more than 10 Japanese companies, a source familiar with the matter has said.

But Japan Industrial Partners failed to meet Toshiba's request to submit a letter of loan commitments from major banks by Monday, the source said, leaving uncertain whether funds can be guaranteed for the takeover estimated at some ¥2.2 trillion in total.

JIP, which leads a consortium that Toshiba designated the preferred bidder for the potential buyout, appears to be basing its total cost estimate on share price, as the figure equals the company's market capitalization, the source said.