A strike by German dockworkers is set to expand on Wednesday, ahead of a fourth round of negotiations between the unions and the port operators. Joining the workers already striking in the major northern ports of Hamburg and Bremerhaven will be colleagues in Wilhelmshaven, Bremen and Emden. Many dockworkers in Hamburg and Bremerhaven have been on a strike since early Tuesday. According to a spokeswoman, around 800 people took part in the industrial action in Bremerhaven. In Hamburg, the number of participants was unclear, but a union spokesman said there was a high level of participation. A ra…