Herman Van Rompuy, president of the European Council, said the deal was an important step in regaining international confidence in the Greek economy.
"We hope that it will reassure all the holders of Greek bonds that the eurozone will never let Greece fail," he said. "If there [was] any danger, the other members of the eurozone would intervene."
Under the details of the agreement, financial assistance would be provided to Greece in the event of the country having "very serious difficulties" with its economy.
Member states would provide two-thirds of the money, with the rest coming from the IMF, reports the Financial Times.
The deal will be regarded as a victory of sorts for German chancellor Angela Merkel - earlier this week she demanded that the IMF make a "substantial" contribution to any potential rescue package.
By Tony Aynsley