The UFO union, which represents 18,000 Lufthansa (LHAG.DE) flight attendants, said it would give only a few hours' notice at most of the strikes, raising a threat to the airline's services, although it ruled out any action for Tuesday.

The dispute is the latest for Lufthansa as it grapples with rising costs, tough competition and economic uncertainties. Costs of a drawn-out stoppage could quickly mount for the airline, which said in 2010 a four-day strike by pilots would cost it 25 million euros a day in lost revenue.

Earlier this year, it put its costs from a strike of airfield employees at its main hub in Frankfurt in the high tens of millions of euros.

The union - which wants a 5 percent pay rise for its members after a three-year pay freeze - had last week called on members to start preparing for a strike so it could take action as swiftly as possible.

Negotiations between the union and Lufthansa, Germany's leading airline, to end a 13-month pay dispute broke down late on Monday.

Lufthansa, which typically operates around 1,850 flights a day, said it still wanted to negotiate a deal with the union, which has also called for a better profit-sharing scheme and guarantees that jobs will not be outsourced or given to temporary workers.

INVESTMENT FREEZE

It said it would give details of its contingency plans only when the union gave strike times, and would do everything possible to minimise disruption. The airline is due to hold a press conference at 1100 GMT.

The move comes as Lufthansa cuts 3,500 jobs - about 3 percent of its global workforce of 117,000 - and freezes investment, aiming to boost earnings which had been squeezed by soaring fuel prices and competition from low-cost and Middle East carriers.

Lufthansa has also shifted the contracts of pilots and flight attendants at carrier Austrian Airlines to a lower-cost subsidiary and has boosted cooperation between its main Lufthansa brand and low-cost carrier Germanwings.

While UFO has said that any airline paying a dividend does not need such drastic cuts, Lufthansa executives had last week defended the savings plan, saying the airline needed to take action to maintain its position in Europe.

Lufthansa shares were down 1.6 percent at 9.75 euros by 0952 GMT, underperforming Germany's blue-chip DAX index .GDAXI, which was 0.4 percent lower. Shares in Fraport (FRAG.DE), the operator of Frankfurt airport and also potentially affected by flight cancellations, were down 0.4 percent. (Reporting by Peter Maushagen; Writing by Maria Sheahan and Marilyn Gerlach; Editing by Dan Lalor and David Holmes)

• A Permanent Economic Emergency