Citing record profits at the German airline, the Verdi union is calling for a 6 percent pay increase for 12 months for workers it represents in ground services, IT, maintenance and cargo divisions, plus some cabin crew.

At a third round of talks on Monday, Lufthansa improved its offer to a 2.6 percent increase for 18 months and 2.5 percent for the following 18 months, which Verdi rejected as too low.The union has also balked at Lufthansa's demand that the pay rise from July 2019 onward be made conditional on the group's profitability, and that workers at airline catering firm LSG get only a one-time payment rather than a wage increase.

While the Lufthansa Group's operating profit rose 4.5 percent in the first nine months of 2017 and is expected to reach a record of nearly 3 billion euros (2.64 billion pounds) for the full year, LSG's nine-month profit dropped by more than a quarter due to the costs of a reorganisation.

"If the next round of talks on Jan. 30/31 does not bring any result, then strikes shall no longer be ruled out," Verdi's chief negotiator Christine Behle said in a statement.

Lufthansa, which was beset by a series of strikes by pilots over a pay dispute in the past couple of years, said it regretted that no progress had been made in this week's talks.

"Lufthansa is still confident that an agreement can be reached in negotiations," a spokeswoman for the company said.

(Reporting by Maria Sheahan; Editing by Douglas Busvine and Susan Fenton)