The union representing German pilots in collective bargaining talks with Deutsche Lufthansa has called a members' strike ballot after negotiations stalled, the Spiegel weekly reported on Thursday, citing a union official.

"If (management) makes good offers, these will resonate with us pilots. But if these offers fail to materialise, we have little choice but to strike," Marcel Groels of the Vereinigung Cockpit pilots' union was quoted as saying.

The union is demanding a 5.5% pay rise this year for its pilots and automatic inflation compensation thereafter, as well as a uniform pay structure for all staff.

Lufthansa was already rocked by strike action held by its ground staff on Wednesday, forcing the German flagship carrier to cancel more than 1,000 flights during the busy summer travel season. (Writing by Rachel More, Editing by Miranda Murray)