The union will announce more details on Wednesday at 1400 CET (8.00 a.m. ET), a UFO spokesman told Reuters.

The flight attendants' union had said earlier it was looking into the possibility of staging strikes lasting for an indefinite period.

The dispute includes pay and working conditions at Lufthansa and led to walkouts staged by UFO last year.

(Reporting by Klaus Lauer; Writing by Michael Nienaber; Editing by Catherine Evans)