With the Swiss team's Russian saviour deal still waiting to be finalised, Bild am Sonntag newspaper reports that Sauber's debts still stand at EUR 80 million, including unpaid bills to suppliers totalling 35 million.
"The time bomb is ticking," the newspaper's correspondents Helmut Uhl and Frank Schneider report.
They claim that, in addition to Ferrari's unpaid customer engine bill, Sauber has also not paid for its Pirelli tyres in 2013.
It was already known that lead driver Nico Hulkenberg is waiting for his pay, but Bild am Sonntag now reports that rookie teammate Esteban Gutierrez has also not been paid in 2013.
And the report said 2012 Sauber driver Kamui Kobayashi is also owed about EUR 2.5 million.
Reportedly, the already delayed Russian saviour deal is also further in doubt due to the uncertain future job prospects of one of the key figures, Oleg Sirotkin.
That's because if Sirotkin's son, 17-year-old Sergey Sirotkin, does not debut as expected in 2014, the entire Russian deal could be off.
Correspondents Uhl and Schneider report that Sauber might need to consider a 'plan B' -- the sale of the Hinwil based team.
Former Force India and HRT boss Colin Kolles is apparently ready on the sidelines with sponsor millions to exchange for a stake in the Swiss outfit.