BRUSSELS (AP) -- The chairman of the Eurogroup says eurozone finance ministers have agreed that banks need to take substantial losses on their Greek bondholdings.

Jean-Claude Juncker said Saturday that "yesterday we agreed that we need a substantial increase in the contribution from the banks."

Juncker, who is also the prime minister of Luxembourg, did not say how big the cuts would have to be.

In July, banks had tentatively agreed to take a loss of about 21 percent on Greek bonds, but it has since become clear that that is not enough to make Greece's massive debts sustainable.

Austria's Finance Minister Maria Fekter said the chief negotiator for the eurozone has been asked to restart negotiations with banks.

That suggests that the eurozone is still aiming for a voluntary deal with banks.

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