The International Monetary Fund (IMF) has ruled out giving Greece an extension for its debt repayment.
Greece has to repay the IMF about 1 billion euros ($1.1 billion) by early May.
IMF Managing Director Christine Lagarde suggested the issue had been raised - and had been flatly rejected.
"We have been able to express and explain the policy of the IMF in terms of payment delays, and give the precedence and history about that to (Greek Finance Minister) Mr Varoufakis," Lagarde said.
"Payment delays have not been granted by the board of the IMF in the last 30 years.
"It's clearly not a course of action that would actually fit, or be recommendable in the current situation."
Athens denied reports that it had asked to put off the repayments to the IMF to buy time.
Greece's plight overtook the spring meetings of the IMF and World Bank, which were meant to discuss the progress of the world economy and the fight against poverty.
On top of its looming debt repayment to the IMF, Greece has another payment due to the European Central Bank in June.
Speculation of a Greek default and a potential exit from the euro mounted after Lagarde's comments.
Greece is struggling to meet its debt obligations on a weekly basis, and the situation is coming to a head.
Its creditors, the IMF and the EU, want Greece to agree to a list of economic reforms that the country's new government came to power promising to oppose.
However, both Athens and rescue creditors concede that a breakthrough is unlikely by an end-of-April deadline they set to unlock a batch of bailout loans, delayed from last summer and worth 7.2 billion euros ($7.7 billion).
Spending cuts spark protests
Meanwhile, the Greek government was forced to announce 177 million euros in new ministerial spending cuts.
At the same time, thousands of miners took to the streets in Athens over fears of losing their jobs, in one of the biggest labour protests since Alexis Tsipras's leftist Syriza party took power in January promising an end to the austerity that came with the IMF-EU bailouts.
Seeking more sources of money, Tsipras on Thursday announced the start of a "dialogue" with the powerful Greek Orthodox Church on using the church's assets to boost the struggling state coffers.
Greece repaid 460 million euros ($495m) to the IMF earlier this month.