Greece is considering slapping a €162 billion invoice on Germany as compensation for the Second World War.
Athens has compiled a top-secret report that says the cash - enough to solve the Greeks' debt crisis - is owed in war reparations, Der Spiegel reported.
The cash would help with Greece's debts
But the Greeks are said to be reluctant to take on mighty Germany over the debt, for fear of antagonising its Eurozone paymaster.
The Greek media is said to be more bullish, with the To Vima newspaper headlined: "What Germany Owes Us".
It set out a number of possible ways that Germany could repay the cash, after a panel of experts spent months preparing the 80-page classified report.
Details of its findings were leaked to To Vima, Der Spiegel said.
Its conclusion was that "Greece never received any compensation, either for the loans it was forced to provide to Germany or for the damages it suffered during the war."
A wealth of archive material was studied as part of the assessment, and the total includes cash for the reconstruction of infrastructure, and the repayment of 'forced loans'.
Athens, whilst reserving the right to take action in the future, was said to be wary of pressing ahead with a demand for payment.
Der Spiegel quoted a senior government official saying: "This is no time to pick a fight with Berlin."