France is committed to nationalise a steel plant at the centre of a bitter row between the government and its owner ArcelorMittal, unions said on Wednesday. Arnaud Montebourg, the minister for industrial renewal, \"told us that if Mittal doesn\'t reverse course, the nationalisation will happen,\" said FO union representative Walter Broccoli. The Socialist government has threatened to nationalise the Florange plant in northeastern France if the company goes ahead with plans to permanently close two blast furnaces on the site that the company regards as uneconomic. ArcelorMittal, which wants to continue to operate the rest of the site, has given the government until Saturday to find a new investor willing to take over the furnaces. Montebourg earlier told parliament an unidentified investor who was already involved in the steel industry had offered to put nearly 400 million euros into the site. \"We have a buyer, who is a steelman, an industrialist, who is not a financier, who wants to invest his own money and who is ready to put almost 400 million euros into renovating this plant,\" Montebourg told deputies. The minister told the same to unions at a meeting later at his ministry. \"It\'s too good to be true,\" said CFDT unionist Edouard Martin after the talks. \"Everything is ready, the financial set-up is solid, they\'re ready.\" President Francois Hollande met Tuesday with the company\'s owner Lakshmi Mittal and warned him that nationalisation was being seriously considered by the government. ArcelorMittal argues that the blast furnaces at Florange are uncompetitive in current market conditions, partly because they are too far from ports for transportation. The company has warned that nationalisation of the plant would cast doubt on the future of all its operations in France, where it employs 20,000 people. Montebourg caused controversy earlier in the week when he said Mittal was not welcome in France, comments that were quickly disowned by his colleagues and from which he subsequently backtracked. Former premier Alain Juppe, a heavyweight figure in the right-wing opposition, called Wednesday for Montebourg to be sacked over remarks he deemed \"calamitous\" for the image of France. \"It is time to replace someone who is on his way to becoming the minister for industrial collapse,\" Juppe wrote in his blog.