FILE PHOTO: Henri Poupart-Lafarge, Chairman and Chief Executive Officer of Alstom, and Siemens President and CEO Joe Kaeser attend a news conference to announce their deal to merge their rail operations, creating a European champion, in Paris, France, September 27, 2017. REUTERS/Stephane Mahe/File Photo

MUNICH (Reuters) - Siemens SIEGn.DE Chief Executive Joe Kaeser said on Monday it was important to have a dialogue based on trust with European Competition Commissioner Margrethe Vestager about a planned merger of Siemens' and Alstom's ALSO.PA rail businesses.

France and Germany on Monday raised pressure on Vestager to approve the merger, warning that thwarting the proposed European champion would be a strategic error.