Employees at Amazon warehouses in Germany started a new three-day strike on Monday to voice their demands for better pay and conditions as the retailer tries to get Christmas orders out on time before next week.

Labor union Verdi said the strike started at five of Amazon's nine centers in Germany added that it would only know later in the day how many workers participated.

The walkouts will run until the end of Wednesday's late shift at the earliest, according to Reuters.

Verdi said that delivery delays could not be ruled out thanks to the strikes, but Amazon customers can order up until midnight on Dec. 21 to get their gifts in time for Christmas. For express deliveries, some orders can be placed as late as Dec. 23 or 24.

"We deliver reliably," an Amazon spokeswoman said this weekend when asked about the strikes.

In 2013, Amazon orders placed in Germany peaked on Dec. 15 when customers purchased approximately 4.6 million items, or 53 items per second.

The U.S. company employs nearly 10,000 warehouse staff in Germany, its second-largest market in the world, plus 10,000 additional seasonal workers.

Verdi has put together a number of different strikes at Amazon since May 2013 as it tries to force Amazon to raise pay for workers at its distribution centers in accordance with collective bargaining agreements across Germany.

Amazon has rejected multiple demands made by the union, claiming it regards warehouse staff as logistics works and they receive above-average pay by the standards of that industry. Employees feel that they earn lower wages than others in retail and mail-order jobs.

The company previously said the long-running dispute hasn't affected deliveries as a large number of workers in Germany haven't joined the strikes and it can draw on a European network of 28 warehouses in seven countries.

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