The European Union has approved a deal under which General Electric will acquire the energy business of French company Alstom for $12 billion, a source close to the transaction said Monday.

In order to win the green light from the European Commission, GE had to make concessions, the source said. EU regulators had expressed concern the deal could lead to too much concentration in the gas-turbine sector.

A formal announcement is expected Tuesday, the source said. It would end months of uncertainty and tension over the proposed deal, part of a drive by the American conglomerate to stake more of its future on industrial operations.