The union called on its members in the German states of Baden-Wrttemberg, Berlin and Brandenburg to vote after wage negotiations failed last week. The results of the ballot should be known by the beginning of next week.
As well as the Wiesloch sheetfed plant in Baden-Wrttemberg, which employs 7,000, other Heidelberg plants that could be affected include Amstetten and Brandenburg, which employ 1,350 and 760 respectively.
A spokesman for Heidelberg said: A strike would hurt all German industry, but we are confident it wouldnt hurt our customer relationships or deadlines.
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