European Commission President Jose Manuel Barroso says the EU needs to agree as soon as possible on a mechanism to support Greece financially if needed.

Greece warned on Thursday that it will be forced to turn to the International Monetary Fund if the EU can't agree to a bailout plan next week that will help reduce its market borrowing rates.

Clashes between riot police and rock-throwing, masked youths broke out during a demonstration on Thursday in central Athens by tens of thousands of striking workers protesting austerity measures that the Greek government has said it has no choice but to implement.

President Barack Obama stood with Greek Prime Minister George Papandreou on Tuesday and pledged that the United States would work with its ally, even as Greece's enormous debts sparked frenzied trading.

Greek Prime Minister George Papandreou on Friday launched a diplomatic quest for concrete support from European leaders in fighting off his country's debt crisis, as workers back home shut down hospitals, schools and public transport to protest painful cuts.