BERLIN (Reuters) - Berlin will negotiate with Athens "until the last minute", a senior ally of Chancellor Angela Merkel told Germany's Inforadio on Friday, but stressed that Greece must be prepared to carry out reforms.

Euro zone leaders will hold an emergency summit on Monday to try to avert a Greek default after bank withdrawals accelerated and government revenue slumped as Athens and its international creditors remain deadlocked over a debt deal.

Peter Altmaier, Merkel's chief of staff, said he still believed it was possible that Athens and its international lenders could reach a solution to Greece's debt crisis.

"We will negotiate until the last minute," Altmaier told Inforadio, adding that the German government did not want "the people in Greece to be disadvantaged because their government possibly did not recognize in time that the hour has come."

At talks in Luxembourg on Thursday finance ministers of the 19-nation euro zone failed to make any breakthrough on a cash-for-reforms deal. Just 12 days remain before Greece must make a crucial debt repayment to the International Monetary Fund.

Altmaier said all EU member states wanted to hold the euro together, but stressed the need for Greece to present sensible reforms.

He said Germany, the IMF, the European Commission and the European Central Bank were all in agreement, adding there was hope "that Greece ... will finally behave like other countries such as Spain, Portugal and Ireland did in the past".

Merkel's chief of staff held out hope for a deal with Athens despite an opinion poll published last week showing that a narrow majority of Germans now want Greece to leave the euro zone.

The chancellor also faces growing opposition among her ruling conservatives to granting Greece any further bailout funds. Germany is Greece's biggest creditor and the biggest contributor to the EU budget and the euro zone bailout fund.

In a sign that Germany's business community is also frustrated with the uncertainty around Greece, the chief executive to German drugs and chemicals Bayer <BAYGn.DE> said politicians needed to make a decision about Athens' future.

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"We have found ourselves in uncertain surroundings in Europe for some years," Bayer chief Marijn Dekkers told mass-selling daily Bild.

"That is a situation that must not continue," he added. "Therefore a decision must now be taken on Greece that is sustainable for years."





(Reporting by Caroline Copley and Paul Carrel; Editing by Gareth Jones)