The International Monetary Fund (IMF) says Greece needs to take more action to promote growth and deliver promised structural reform.
On Monday it backed the next payment of 1.7bn euros (£1.5bn: $2.3bn) after its fourth review of the country.
But now it says Greece must deliver "rapidly on structural reforms to unlock growth and create jobs",
It also pointed to a potential 10.9bn euros "financing gap" over the next two years.
Greece was granted a huge 110bn euro (£93bn; $145bn) IMF/EU bailout in May 2010.