A union representing pilots at Germany's Lufthansa says talks aimed at resolving a dispute over early retirement benefits have broken down and is threatening further strikes.

The Vereinigung Cockpit union staged three strikes, each of which lasted for several hours, in recent weeks against Lufthansa and its Germanwings subsidiary. However, a fourth strike planned for Sept. 16 after receiving a new offer from the airline.

The union said Thursday it "regrets that the negotiations have failed again." It said more walkouts can be expected though no dates were given.

The two sides are at odds over the pilots' demand that Lufthansa keep a transition payment for those wanting early retirement.

The airline, which faces tough competition from European budget airlines and major Gulf carriers, wants to cut those payments.