For Toshiba, which was demoted to the second section of the Tokyo bourse this month, a loss of its status as a listed company would further complicate its ability to raise money, particularly for the investment-intensive chip business that it is trying to sell.

Since taking over as Toshiba's auditor in June last year, PricewaterhouseCoopers Aarata (PwC) has yet to endorse the firm's financial results which have suffered numerous delays.

In particular, PwC has queried whether Toshiba should have recognized multi-billion dollar losses at U.S. nuclear arm Westinghouse earlier than last December, sources familiar with the matter have said.

PwC is now looking at issuing an "opinion with qualifications" - given where only minor problems exist - by a bourse-imposed deadline on Thursday, but it could also still issue an "adverse opinion", Jiji news agency said, without citing sources.

Toshiba has entered discussions with the auditor, seeking to gain an opinion with qualifications, Jiji added.

The Nikkan Kogyo business daily reported that PwC could also issue a stronger "opinion without qualifications," which is given where no problems are found in a company's accounts.

Neither report stated the reasoning behind a possible endorsement from PwC. PwC and Toshiba declined to comment.

Shares in Toshiba jumped 6 percent on the reports, increasing its market capitalization to 1.13 trillion yen ($10.2 billion).

A writedown at Westinghouse and other liabilities linked to the nuclear unit have pushed Toshiba into negative shareholders' equity of $5.2 billion, triggering its demotion to the second section of the bourse and forcing it to put its $18 billion chip unit up for sale.

An auditor endorsement may remove one less headache for Toshiba has it seeks to close the memory chip unit deal that has stalled due to disagreements between members of the main bidding groups. Toshiba will, however, still be automatically delisted if it ends the current year with negative shareholders' equity.

"It's a necessary step forward - but not a sufficient step forward – to resolve the list of uncertainties," said Macquarie analyst Damian Thong.

"The sale of Toshiba Memory is something that's much more significant to the future of the company," he said.

(Reporting by Thomas Wilson; Additional reporting by Makiko Yamazaki; Editing by Edwina Gibbs)

By Thomas Wilson