Meanwhile, budget airline Ryanair said it was ready to operate Alitalia's routes in Italy.
The outspoken head of Ryanair, Michael O'Leary, told Italy's Corriere della Sera newspaper on Friday that his budget airline was ready to step in a
replace Alitalia on its domestic routes if the carrier went bankrupt. He said Alitalia had been ruined by politics and unions.
Lupi said on public radio Rai: "We believe that Italy is an essential country for international air travel because we are a major industrial country and we have designated Air France as our principal partner."
He characterised as critical Alitalia's capital increase of €300 million to be decided at a board meeting which began at 1200 GMT on Friday.
"Let's see what Air France does, otherwise I believe Alitalia's task will be to find another big international partner," said Lupi.
Alitalia had been threatened with being grounded this weekend if the capital increase did not succeed, but late on Thursday the Italian government announced the postal service would step in and inject €75 million.
That investment should allow Alitalia to pay fuel suppliers, which had threatened to halt deliveries on Saturday, a move that would force regulators to ground the airline completely and likely pus it into bankruptcy.
But Poste Italiane's investment forces Air France-KLM to show its cards.
Air France-KLM's chief Alexandre de Juniac told Les Echos newspaper last week that that the group, which is still losing money and going through a painful restructuring of its own, was willing to help out Alitalia only under strict conditions.
Air France-KLM is currently the leading shareholder with a 25-percent stake. To keep that level it must inject 75 million euros or see its holding fall to 11 percent.
When announcing Poste Italiane's investment into Alitalia the government said there would have to be "a major overhaul of the industrial plan".
However the government has previously stymied attempts by Air France-KLM to take over Alitalia, which needs deep restructuring that would put the jobs of many of its 14,000 employees on the line.
Alitalia reported net losses of €294 million in the first half of this year, compared to a €201 million loss over the same period in 2012.