A parallel special purpose fund or funds will be established, which will buy government bonds from struggling eurozone countries.
The International Monetary Fund (IMF), Japan and China will be asked to participate.
But on the eve of the summit to be held in France this week pressure was mounting on the US - itself battling recession - to drum up support for the eurozone.
Already questions have been raised over whether the rescue fund will work. For a start, it is not clear whether the IMF has agreed to participate.
On Saturday, Italy's borrowing costs soared to their highest levels since it joined the euro, an unsustainable 6.06 per cent, a signal that the market has little faith in plans to curb the crisis.
Silvio Berlusconi, Italy's scandal-hit Prime Minister, did not help by describing the euro as a strange currency that was undermining an otherwise strong economy.
How the new bonds will work and their interest rates will not be set until January, effectively making the EFSF agreement a hypothetical exercise for the next three months.
- Independent