Eleven Latin American nations have refused to support the International Monetary Fund's repeated bail-outs for Greece, after citing concerns that the country won't be able to pay its creditors back.
In a rare public declaration, Brazil's executive director at the IMF, who also represents 10 small nations in Central and South America and the Caribbean, said the countries were fed up of bankrolling the sovereign debt crisis-hit country and other European nations.
"Recent developments in Greece confirm some of our worst fears. Implementation (of Greece's reform programme) has been unsatisfactory in almost all areas; growth and debt sustainability assumptions continue to be over-optimistic," said Paulo Nogueira Batista.
Batista added that there was a severe risk that Greece would not be able to pay back the €240bn (£210bn, $318bn) it will borrow in emergency funds from the IMF, European Union and the European Central Bank, if Greek reforms derail and EU governments withdraw their support.
Greece has so far siphoned €28.4bn from the IMF and on Monday the country received a tranche of €1.7bn.
The IMF report, published on Wednesday, said if this does happen then Athens' "capacity to repay the Fund would likely be insufficient".
"This statement is one step short of openly contemplating the possibility of a default or payment delays by Greece on its liabilities to the IMF," said Batista.
Greece has already used up almost 90% of its total emergency funds and it still teeters on the brink of collapse.
Unemployment is the highest in Europe, with over a quarter of the Greek population without a job, while public sector reforms will see jobless rates rise further.
The eurozone has pledged to consider mild debt cut relief measures for Greece in 2014, such as extending maturities on its rescue loans, to reduce its debt-to-GDP-ratio to 120% by 2020.
However, the IMF warned in its report that Greece might need faster debt relief from Europe, in order to spur investor confidence and achieve the annual growth rates of about 3%.