Arcelor's Indian CEO Lakshmi Mittal was no longer welcome in France, has said an unnamed industrialist was ready to inject 400 million euros into the site.
Montebourg huddled in a cafe with a group of orange-vested metal workers protesting near the finance ministry early on Friday, telling them that nationalisation was still an option.
"He told us that he was not in control of the Elysee's (Hollande's office) agenda but he thinks that a deal will not come today and is more likely tomorrow," Edouard Martin, head of the CFDT trade union's Florange chapter, said.
Recalling Hollande's pledge to save jobs at Florange when he met workers there while campaigning for president, Martin added: "Make sure he doesn't forget the merguez (sausage) he ate with us at Florange on February 24 - he'll understand."
Hollande is wary of the stigma that even a temporary nationalisation would carry abroad and prefers an intermediate solution that would save jobs and draw new investment to Florange, Le Monde daily reported, citing government sources.
Officials have defended a temporary nationalisation of the site, saying it is a special case because ArcelorMittal has broken promises to keep the furnaces running.
But ArcelorMittal denies breaching commitments. Sources close to the group say Arcelor planned in 2003 - before its 2006 takeover by Mittal - to wind down inland blast furnaces in Europe, including the two in Florange, by 2010.
They argue that overcapacity in Europe's steel market, with demand 28 percent below peak 2007 levels, has made Florange's furnaces uneconomical and that a buyer would have to absorb deep losses to take them on, even with the rest of the site.
In Rome, the Italian cabinet was reviewing a decree on Friday to secure the future of the troubled ILVA steel plant after discussions between Prime Minister Mario Monti and the management on Thursday.
ILVA is a major employer in a jobs black spot in southern Italy and is threatened with closure over concerns that toxic factory emissions increased deaths from cancer and respiratory diseases in the surrounding area of Taranto.