The French government and steel producer ArcelorMittal are hopeful of closing to a deal to avoid a temporary nationalisation of a steelworkers, ahead of a midnight deadline.
ArcelorMittal, controlled by Britain's richest man Lakshmi Mittal, says two furnaces at the site in north-eastern France are not viable but Socialist President Francois Hollande wants them kept open. The government has threatened to take over the site if no private buyer is found.
The two furnaces together employ 600 workers with the entire site providing work for 2,700.
Earlier this week Mayor of London Boris Johnson called the French government's stance "eccentric" and said ArcelorMittal would be welcome to move production to London.
"The sans-culottes appear to have captured the government in Paris," he added.