Greece's enormous debts are sustainable but on a knife's edge, the International Monetary Fund (IMF) says.
Investors still fear the country will default on its debt despite a €110 billion rescue package being implemented, the BBC reports.
IMF Athens mission chief Poul Thomsen says given the situation, Greece must stick to its reform programme.
"The Greek debt is sustainable but it is, as we say, on a knife's edge,"he told Greek newspaper Ethnos.
The eurozone members will hold a special summit on 21 July discuss the debt crisis and provide fresh aid for Greece.
Greece has passed several rounds of austerity measures, including tax increases, pay cuts, privatisations and public sector redundancies, to get aid from the IMF and the European Union.
Greece has more than €350 billion of debt, and the IMF warned last week than it needs an additional €100 billion in aid on top of last year's bail-out to avoid a default.