The EU and the International Monetary Fund say Greece is making economic progress, but needs to reform faster.
The latest tranche of aid to Greece has been approved, under a rescue package worth up to 110 billion euros ($US145 billion) over three years.
Greece will now receive the next 15 billion euros of the loan.
But the BBC reports the tone of the latest review by the EU, IMF and the European Central Bank was more critical than the last one.
In November, inspectors from the European Union, the European Central Bank and the IMF said Greece needed to make an extra effort to reduce its deficit in 2011, but the government had made impressive savings during a deep recession.
In the latest review, the inspectors said: "While there have been delays in some areas, the underlying fiscal and broader reforms necessary to deliver the programme's medium-term objectives are being put in place.
"However, major reforms still need to be designed and implemented to build a critical mass necessary to secure fiscal sustainability and economic recovery," the EU, ECB and IMF said in a joint statement.
In response, Greece on Saturday accused the EU and IMF of interfering in its domestic affairs.