U.K. labor union RMT plans strikes on Eurostar International Ltd. services this weekend and again in late August to protest what it says is the rail operator’s failure to live up to a scheduling program for train managers.

A four-day walkout will begin in the early hours of Friday and last through midnight on Monday, the union said in a statement Wednesday. Eurostar responded that it will cancel two trains a day “at most” during the period. The second strike will last three days, from Saturday, Aug. 27, through Monday, Aug. 29, the RMT said.

“The dispute centers on Eurostar’s failure to honor an agreement from 2008 which sought to ensure that train managers could expect a good work-life balance in terms of unsocial hours and duty rosters,” the union said.

Eurostar operates high-speed passenger trains linking London with Paris and Brussels via the Channel Tunnel, and it served 10 million travelers in 2015. The company is trying to find a resolution with the RMT, and will make arrangements so that all passengers who have tickets can travel this weekend, a Eurostar spokeswoman said by phone from London.

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This article was written by Phil Serafino from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: A Eurostar e320 train. The operator is preparing for a series of strikes organised by the RMT labour union this summer. Digital News Agency for Eurostar