BERLIN, March 9 (Reuters) - Ground staff at Berlin's two airports will start a 25-hour strike on Friday morning over a pay claim, union Verdi said, stepping up action after several strikes in recent weeks that have forced the cancellation of more than 300 flights.
Workers will walk out at 4 am local time (0300 GMT) on Friday and end the strike at about 0400 GMT on Saturday, said Verdi.
The stoppage, expected after 98.6 percent of balloted workers at Schoenefeld and Tegel airports last week backed industrial action, coincides with the world's biggest tourism trade fair, which ends in Berlin on March 12.
The ITB fair attracted 120,000 trade visitors last year.
Verdi wants an increase in pay for ground staff to 12 euros an hour from about 11 euros as part of a one-year collective agreement.
Carriers including Air Berlin, Lufthansa, easyJet and Ryanair serve the two airports.
Ground staff jobs include checking in passengers, loading and unloading planes and directing aircraft on the tarmac. (Writing by Madeline Chambers; editing by John Stonestreet)