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BRUSSELS/FRANKFURT (Reuters) - Siemens SIEGn.DE and Alstom ALSO.PA are set to face a full-scale EU antitrust investigation this week after declining to provide concessions to allay regulatory concerns about their plan to combine their rail operations, two people familiar with the matter said.

German industrial group Siemens and French rival Alstom want to create a Franco-German rail champion to compete more effectively with bigger rival CRRC and Canada’s Bombardier Transportation.

The companies had until July 6 to offer concessions to the European Commission but did not do so. Some firms prefer to wait for the EU antitrust enforcer to set out possible anti-competitive issues so they can tailor concessions to address them.

The Commission is expected to open a 90-working day investigation on Friday following the end of its preliminary review, the people said.

The Commission and Siemens declined to comment.

Siemens is seeking to convince regulators by citing the competitive threat from CRRC and that it does not compete with Alstom in rolling stocks, trains and signalling technology.

Competitors have expressed scepticism, saying that the two companies are the dominant players in Europe which can squeeze them out after the deal.