The UFO union, which represents around two thirds of Lufthansa's 19,000 cabin crew, would not say on Thursday which locations would be targeted or give the exact timing of strikes, saying only it would give six hours' notice.

Financial Times Deutschland said cabin crew members were preparing to hold the strikes in Frankfurt and Munich, citing UFO sources. It said on its website the union was discussing whether the strikes would also include Berlin.

The strikes come as Lufthansa cuts jobs and implements a three-year cost-cutting programme to boost margins and finance investment in planes in the face of a weakening economy, high fuel costs and increased competition from low-cost carriers.

Germany's leading airline, which operates around 1,850 flights daily mostly from Frankfurt and Munich, needs to generate more profit to pay for 17 billion euros of more fuel-efficient aircraft on order.

Lufthansa (LHAG.DE) and the UFO union have been negotiating for 13 months, with the union demanding a 5 percent pay rise and guarantees that Lufthansa will not outsource jobs and use more temporary workers, as it has already done in Berlin.

Talks broke down on Tuesday, and while Lufthansa has called for further negotiations, it maintains that cabin crew must contribute to the cost-cutting programme.

"It may well be that this industrial action could continue for a very long time," UFO said on its website.

UFO said the first wave of strikes would cover certain airports, rather than nationwide action. It has previously mentioned Berlin, Frankfurt and Munich as likely candidates.

"We do not want to give Lufthansa the opportunity to prepare for the strike by getting replacement crews ready," UFO head Nicoley Baublies told Reuters.

Lufthansa has previously said it would seek to keep disruptions to a minimum by using cabin crew who were not part of the union and by drafting staff from other units.

A spokesman for the airline said it had several strategies to mitigate the impact of striking staff and would prioritise long-haul flights.

Lufthansa estimates a nationwide strike on a busy day would cost it millions of euros. Analysts have said costs could be kept to around 5 million euros a day if flight cancellations were kept to a few hundred. (Reporting by Marilyn Gerlach and Peter Maushagen; Editing by Mark Potter and Helen Massy-Beresford)

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