ATHENS: The Greek central bank warned on Wednesday that the country risked a painful exit from the euro and ultimately even the European Union if Athens and its creditors do not strike a swift aid-for-reforms deal.

A top Greek negotiator told Reuters that Prime Minister Alexis Tsipras' leftist government was ready to make unspecified concessions but he once again ruled out any cuts to pensions — a major sticking point in the negotiations.

Germany, Europe's biggest economy, maintained its line that Greece had to make significant moves to break the stalemate.

Athens has until the end of June to find a way out of the impasse before it faces a 1.6 billion-euro ($1.8 billion) repayment due to the International Monetary Fund, potentially leaving it bankrupt and teetering on the edge of the euro zone.

"It won't work without Greece moving significantly," German Foreign Minister Frank-Walter Steinmeier said in Berlin.

Greek negotiator Euclid Tsakalotos confirmed that Greece does not have the money to repay the IMF and said the government would only accept a deal that was sustainable and addressed debt, financing and investment — issues the European Union has said it does not want to open at this stage.

"If you have that, then the Greek government will sign the deal," Tsakalotos said. "If it doesn't have that kind of deal there is no point in signing onto something that you know is going to fail."

Hopes that a deal might be struck on Thursday at a meeting of European finance ministers looked increasingly remote.

"People are getting anxious on both sides. Athens expects Brussels to move. And Brussels expects Athens to move. And it's stuck," said a senior EU diplomat, who declined to be named. "It's very dangerous, and we may have an accident."

Making clear the huge stakes at play, the Greek central bank said reaching an accord was "an historical imperative" that the country could not ignore.

"Failure to reach an agreement would ... mark the beginning of a painful course that would lead initially to a Greek default and ultimately to the country's exit from the euro area and, most likely, from the European Union," the Bank of Greece said in a monetary policy report.