Vestager is expected to announce the Commission's veto of the planned merger of the rail businesses of Siemens and Alstom, and of a proposed copper deal between Aurubis and Wieland-Werke AG.

The deals are seen as hurting competition, sources told Reuters. Siemens and Alstom had wanted to combine their rail operations to compete more effectively with China's state-owned CRRC Corp Ltd on the global stage.

Aurubis, Europe's biggest copper smelter, was wanting to sell its flat rolled copper products business to Germany's Wieland so it can expand into other metals besides copper.

(Reporting by Foo Yun Chee and Philip Blenkinsop; Editing by Alastair Macdonald)