Fantozzi said the company could not meet payroll obligations beyond this month and that if no "reasonable offer" emerges by noon on September 30, "I will ask for a suspension of the licence, not a revocation, which would be more damaging".
Alitalia, which is 49.9 per cent state-owned, is losing about $4.5m a day, with a debt of around $1.7bn.
In a statement on Alitalia's website, Fantozzi said he was seeking "whoever might be able to assure continuity of the transport service in the medium term ... to indicate interest in the acquisition of one or several branches of Alitalia".
Fantozzi, who was named by the government late last month to manage Alitalia, said flights would be "guaranteed" until September 30 unless Enac revokes the airline's licence.
As with the offer by the Italian Air Company (CAI), a consortium that withdrew its $1.5bn offer for Alitalia last week, any new bidder would not be responsible for the airline's debt, which would fall on the shoulders of the Italian taxpayer.
Six of the airline's nine trade unions rejected a deal proposed by the CAI that would have led to 3,250 job losses.
The Italian General Confederation of Labour (CGIL), which opposed the CAI plan, hailed the quest for new bidders, calling it "a new and positive move".
Guglielmo Epifani, CGIL's leader, said: "Bankruptcy would be a tragedy. Mr Fantozzi is right to look for alternatives."
Four labour unions, including two pilot groups fiercely opposed to the CAI plan, said they were in contact with potential investors to build an alliance around an offer.
They said they would contribute $500m in pension benefits to a new deal.
The government appeared to hold out hope that CAI would return to the negotiating table.
Altero Matteoli, Italy's transport minister, said: "CAI is all there is. If the unions sign on, we can try to renew [discussions]."
|Berlusconi had promised a "miracle" to save Alitalia from bankruptcy [AFP]
The consortium's withdrawal was an embarrassment for Silvio Berlusconi, Italy's prime minister, who last month promised a "miracle" to save Alitalia from bankruptcy.
The airline has been surviving on a loan of $450m made in late April from public funds after takeover talks with Air France-KLM collapsed, also largely due to union resistance.
The European Commission is investigating whether the loan met European Union bail-out rules after expressing grave doubts.
Air France-KLM declined to comment on Monday's developments, while Fantozzi said the German airline Lufthansa, mentioned as a possible saviour in the Italian press, "has not made itself heard".
Berlusconi had made the plight of Alitalia a campaign issue ahead of legislative polls in April, vowing that he would reject an Air France deal "out of hand" if elected in preference for an Italian alternative.