Peter Sauber has blamed BMW's demands for the failure of his negotiations to complete a takeover of the team.
AUTOSPORT understands BMW was asking for much more money for the purchase of its Hinwil base - from which all the team's activities except powertrain development are run - than Sauber was willing to pay.
Sauber, who brought the team into Formula 1 in 1993 and retained a 20 percent stake after it was bought by BMW in 2005, said that had a deal been completed, he would have been able to sign the Concorde Agreement.
This would have guaranteed the team a share of the sport's sport revenue for the next three years and helped ensure its long-term future.
"Following the announcement by BMW that it will be pulling out of Formula 1 at the end of the 2009 season, I tried to launch a takeover and rescue of the team," Sauber told AUTOSPORT.
"However, the negotiations with BMW have failed because the demands were simply far too high for me. Consequently, I have been unable to sign the Concorde Agreement, which guarantees payments worth millions and would have secured the future of the team."
Sauber is still determined to do everything he can to ensure that the Hinwil-based team continues in Formula 1, but described the collapse of the deal as the "bitterest" in his motorsport career.
"I am incredibly disappointed and disconsolate," said Sauber. "For me this is the bitterest day in my 40-year career in motor sport. It is also a devastating setback for the team.
"Other solutions must now be sought. The responsibility for that lies in the hands of BMW. Needless to say, I am willing to help, as before."