BERLIN (AP) -- A union says workers at Lufthansa, Germany's largest airline, will stage one-day strikes Thursday to increase pressure ahead of a new round of wage negotiations.

The ver.di union said Wednesday that it was calling for workers to walk off the job in Frankfurt, Berlin, Hamburg, Munich and other airports. The union and Lufthansa are to meet Friday to discuss ver.di's demand for a 5.2 percent increase over the next year for the 33,000 Lufthansa employees it represents.

It says Lufthansa's call for a two-year pay freeze until January 2015 and the extension of the work week by an hour, as it tries to manage costs amid an increasingly competitive environment in the industry, is "wholly unacceptable."

Short term "warning strikes" are common tactics used by German unions in labor negotiations.