President Francois Hollande defended a deal with ArcelorMittal allowing the world's top steelmaker to close two blast furnaces at its plant in eastern France, as he toured the factory amid jeers from angry workers.
The Florange plant, in the heart of the northeastern Lorraine region, has become a symbol of the decline of France's industrial sector, from which 750,000 jobs have disappeared over the past decade.
Despite a campaign pledge to preserve jobs at plants like Florange, Hollande finally buckled under the costs of reviving it, agreeing to mothball the loss-making furnaces through a November deal that avoided compulsory redundancies.
Hollande, who attracted boos and whistles as his convoy drove into the plant, said: "I wanted to come back to Florange as president to have an eye-to-eye discussion with the representatives of a workforce that has been fighting (to keep the plant open) for more than two years.
"You may not accept or understand the decisions that were made but they were made in the interests of Florange."
The president promised to set up a steel research centre and pledged to provide 20 million euros for it next year.
The president also vowed to return to Florange annually, but union officials were unimpressed.
"He has betrayed us," said the CFDT's Pascal Olivarez.
In the runup to the Florange deal, French authorities briefly threatened to nationalise the site, but backed away from those plans and instead left the fate of the furnaces tied to a decision on a European Union carbon capture project.
Under the November agreement with the French government, ArcelorMittal committed to investing at least 180 million euros ($235 million) in the plant, allowing for part of it to continue making finished steel products for another five years. It also said it would look into the EU-funded "green steel" project known as ULCOS.
But once the papers were signed, ArcelorMittal said it was pulling out of the ULCOS project due to technical difficulties.