The International Monetary Fund is seeking to increase its funds by at least $US500 billion to help stabilise the global economy and aid countries reeling from the eurozone debt crisis.
G20 officials will discuss increasing IMF resources at a meeting in Mexico City on Thursday and Friday.
The IMF said it will need $US500 billion to lend to member countries in need, and IMF sources told the Reuters news agency that another $US100 billion is needed as a "protection buffer."
The IMF also estimated there would be a $US1 trillion global financing gap over the next two years if global economic conditions worsened considerably.
However some nations say Europe must first do more itself to support its ailing members.
The governor of the Bank of Canada, Mark Carney, says it is not clear that European governments have done everything necessary to fix their economies.
Eurozone nations have promised to inject an extra €150 billion into the IMF, which is included in the total estimate.