EU ambassadors to Sofia, who have just been told of the plan, are also sceptical.

Usually, the company that will be in charge when the deal is complete notifies the commission, but Arcelor and Severstal do not seem to agree on this central question.

Article 50 of the Treaty on the Functioning of the EU foresees the procedure to be followed in case a Member State notifies the European Council of its decision to withdraw from the Union.