Amazon.com Inc. (AMZN) workers in Germany sent a delegation to the company’s Seattle headquarters to reinforce strikes demanding higher pay and a better work environment, the Verdi union said.

Union representatives will be joined today in Seattle by members of U.S. unions including the Communications Workers of America, Verdi spokesman Heiner Reimann said. Workers at the German logistics centers in Bad Hersfeld, Leipzig and Graben have been called to go on strike today, the union said.

“Amazon is trying to completely ignore us,” Reimann said by phone from Bad Hersfeld. “Today we’re showing that we’re not isolated, that support is growing and that we’re working to stay on the company’s agenda.”

Strikes began in May, with demands including collective wage agreements, increases in minimum pay and better treatment of employees. Amazon, whose headcount rose to 88,400 at the end of last year from 56,200 a year earlier, has built new logistics centers and hired workers on temporary contracts to soften the impact from the strikes on year-end holiday shipments.

Employees in Amazon’s nine German logistics centers receive an income “at the upper end of what is the norm in the logistics industry,” Anette Nachbar, a spokeswoman for the company in Munich, said by e-mail. “We see no advantage for our employees from entering into a collective wage agreement that Verdi demands.”

Amazon is using its “entire European logistics network” to make sure customers receive deliveries for the holidays, Nachbar said. The majority of workers in Germany worked regularly throughout the strikes so far, she said.