The head of the International Monetary Fund has signalled that the organisation will not agree to let Greece delay a scheduled bailout payment.
IMF Managing Director Christine Lagarde said it needed to protect its sterling reputation as a global lender.
Greece is fast running out of cash and its eurozone and IMF lenders have frozen bailout aid until the new government in Athens reaches agreement on a package of reforms.
That has raised fears the Greek government will not be able to make its next payments to the IMF, which total €930m over the next month.
"We have never had an advanced economy asking for payment delays," Ms Lagarde said in response to reporters' questions on Greece's debt crisis.
Asked whether that meant the IMF would not grant a delay if Greece asked for one, Ms Lagarde answered indirectly.
"I can assure you that (IMF) management will do everything it can to make sure that lending to the fund is actually the safest lending route that anyone can go," she said at a briefing ahead of the IMF and World Bank spring meetings.
Speaking earlier in Washington, EU Economic and Monetary Affairs Commissioner Pierre Moscovici said the financial fallout from a potential Greek exit from the eurozone could be contained.
But he said an exit would present a political rupture that would raise questions about who may be next.
"It would be a catastrophe for the euro zone," he said.
Ms Lagarde, who later met Greek Finance Minister Yanis Varoufakis, in the briefing said Greece and its lenders need to "get on with the work" of evaluating Greece's reform plans and coming to an agreement.
"To do that, it's not done by a political, last-minute accord," she said. "It's done by ... the tedious work of financial ministers, wherever they are, and the lenders."
Mr Varoufakis said Greece cannot simply sign up for an existing agreement on its debt that will not solve its economic problems.
He said: "We will not sign up to targets we know our economy cannot meet by means of policies that our partners should not wish to impose.
"We will compromise, we will compromise and we will compromise in order to come to a speedy agreement.
"But we are not going to end up 'being' compromised. This is not what we were elected for."
