Berlin's much-delayed new airport needs up to EUR 1 billion in extra funds before it can open, German newspaper Bild am Sonntag said on Sunday, in what would be another setback for the project which is expected to open in October 2020.

The report said the management of Flughafen Berlin Brandenburg GmbH (FBB), which runs Berlin's airports, had told the supervisory board before Christmas how much more money it would need.

No one at FBB was immediately available to comment when contacted by Reuters.

The Bild am Sonntag report said the airport's construction costs and lost revenues alone amounted to EUR 25 million(US$30 million) per month. This would mean a funding gap of around EUR 750 million up to the planned opening date in October 2020, the report said.

In addition, further funds are needed to finish the airport and to speed up its expansion, the report said.

Plans to open the airport in June 2012 were called off with just three weeks' notice, and when it does finally open it will not have enough capacity.

Berlin's Tegel and Schoenefeld airports served 33 million passengers in 2016, but the new hub is set for an initial capacity of just 27 million.

Bild am Sonntag cited shareholder sources as saying the airport could raise a maximum of EUR 400 million through loans. The newspaper said the shareholders - the states of Berlin and Brandenburg and the federal government - disagree on how to raise the rest.

In December, Engelbert Luetke Daldrup, the airport's CEO, said the airport would need extra funds and the supervisory board would discuss the how to raise the money in early March.