German Chancellor Angela Merkel is facing growing opposition among her ruling conservatives to granting Greece any further bailout funds, increasing pressure on her to drive a hard bargain with Athens.
German lawmakers are highly unlikely to veto any extension of bailout funds to Greece thanks to support for the aid from the Social Democrats, who rule in a 'grand coalition' with Merkel's conservatives, and from the opposition Greens.
But Athens' unwillingness to accept further economic reforms is turning a growing minority of Merkel's own conservatives against the prospect of unlocking a final tranche of Greece's second bailout or agreeing to a third aid programme.
"The recent months have made me sceptical that the Greeks are really ready to tackle these significant reforms," said Hendrik Hoppenstedt, a CDU lawmaker from Hanover.
"At the moment, I feel the Greek government is playing a high-stakes game," added Hoppenstedt, who voted 'yes' in February to an extension of Greece's second bailout.
Then, German lawmakers approved the extension but a record number of conservative dissenters underscored the scepticism in Berlin about whether Athens can be trusted to deliver reforms.
Of 32 "no" votes, 29 came from Merkel's Christian Democrats (CDU) and their sister party, the Bavarian Christian Social Union (CSU).
Moreover, 109 conservatives signed statements saying they had voted for the extension but with reservations.
The negotiating tactics that Greek Prime Minister Alexis Tsipras' leftist government has since employed have further frustrated the conservative German lawmakers.
Michael Frieser, a CSU lawmaker from Nuremberg who voted in favour of the bailout extension in February, said Greece had squandered the time it was given then and that, without reforms, any further aid to Athens would be wasted.
"Now is not the time to talk about a further aid programme and I could not vote for one because it would not be help for self-help but rather sustenance for a system that doesn't work," he said.
Athens is likely to default on a 1.6 billion euro repayment due to the International Monetary Fund at the end of June unless it receives fresh funds from its frozen bailout or the European Central Bank lets it sell more short-term debt to Greek banks.
That will only happen if the two sides can agree in the coming days on a cash-for-reforms deal that has been the focus of acrimonious negotiations for the last four months.
The resistance in her own party to granting Athens more aid means Merkel must take a hard line in talks with Tsipras.
"This just adds to the debtor-creditor stand-off," said David Marsh, managing director at think-tank OMFIF in London.
"Both sides are drawing themselves into implacable positions."
The chancellor said on Wednesday she and French President Francois Hollande were ready to talk to Tsipras in Brussels if the Greek prime minister wished to, and their message would be that talks with international creditors -- the IMF, European Commission and ECB -- must continue.
"The goal is, we want to keep Greece in the euro zone," she said. "Where there is a will, there is a way."