Margrethe Vestager is due to give her decision on the proposed mega-merger by Feb. 18.

"We are talking about two great companies that are able to compete in the market," Vestager told German newspaper Die Zeit in an interview to be published on Thursday.

The two companies' plan to create a European rail champion to take on a Chinese rival has failed to win over EU antitrust regulators despite German and French backing, people familiar with the matter told Reuters on Friday.

The deal would create the world's second-largest rail company with combined revenues of around 15 billion euros (13.12 billion pounds), roughly half the size of China's state-owned CRRC Corp Ltd but twice the size of Canada's Bombardier.

Vestager told the newspaper it was too early to speak about the result of the European Commission's investigation.

She said the Commission had looked in depth at how the market was developing as well as the impact of competition on customers.

"We have closely examined the Chinese presence in the market. Alstom and Siemens are already world champions in their businesses, not only European champions," Vestager said.

Vestager also said that the rail signalling business was a very sensitive topic because of its importance for rail safety.

(Reporting by John Revill and Tassilo Hummel; editing by Thomas Seythal and Michael Shields)