A union representing German train drivers has called members out on a five-day strike starting Tuesday — its longest walkout yet in an increasingly bitter dispute with the national railway operator.

The GDL union said passenger train drivers will walk off the job at 2 a.m. (0000 GMT) Tuesday and won't return until 9 a.m. (0700 GMT) on May 10. Freight train drivers will start their walkout Monday.

GDL and railway operator Deutsche Bahn are locked in a long-running dispute in which the main sticking point is GDL's demand to negotiate not just for train drivers but for other railway staff traditionally represented by a larger rival union.

During previous walkouts, Deutsche Bahn has kept a limited number of trains running on key routes but there have been widespread cancelations.