The international airport, which was originally due to open in 2012, has been under construction since 2006. Despite Germany's reputation for engineering and organisational prowess, red tape and technical problems have repeatedly delayed its inauguration.

German daily Bild had reported on Wednesday that the opening had been pushed back a fifth time due to problems with electrical systems, citing sources close to the airport and its owners.

It had said the fresh delay would be announced in the second half of January.

Chief Executive Karsten Muehlenfeld told daily Der Tagesspiegel that no decision had been made to postpone the opening now set for late 2017 but that the airport still needed regulatory approval for an amendment to its building permit and had to finish construction of the passenger terminal.

"I don't want to hide the fact that the risks prevail by now. The chance (of opening in 2017) is only very small now," Tagesspiegel quoted Muehlenfeld as saying.

Any official opening next year would have to happen by October or November, he said, as an overnight move from Berlin's Tegel airport in west Berlin in the winter, when there might be snow and ice, would be too risky.

"Then it would happen at the earliest when the flight schedules change, so in late March," he said.

The new airport, named after the late politician Willy Brandt, is jointly owned by the federal government as well as the state governments of Berlin and Brandenburg. Companies involved in the construction include German engineering groups Siemens and Bosch [ROBG.UL].

(Reporting by Maria Sheahan; Editing by Erik Kirschbaum and Raissa Kasolowsky)