The Commission in July opened a probe, saying the deal which could create a global leader with three times the market share of its closest rival, could reduce competition and lead to higher fares for travelers.

"People are coming to us with concerns saying that this would be a very big company in Europe. The analysis is still ongoing. We hope anyone with concerns will come forward to us. It is not too late. Please come forward if there are any concerns," Vestager told a European Parliament hearing.

German industrial group Siemens and French rival Alstom announced the planned rail merger in September last year, an industrial boost for French President Emmanuel Macron which, however, has prompted criticism from opposition politicians.

Vestager said her investigation would look into the role of other big global companies in Europe and whether these would provide a competitive constraint to the merged company.

Siemens and Alstom have defended their deal, saying it was necessary to stave off the competitive threat from bigger Chinese rival CRRC (China Railway Rolling Stock Corporation) and Canada's Bombardier Transportation.

The European Commission will decide by Jan. 28 whether to clear the deal. The deadline can be extended should the companies offer concessions.

(Reporting by Foo Yun Chee; editing by Emelia Sithole-Matarise)

By Foo Yun Chee

Stocks treated in this article : Alstom, Siemens