The charities that provide food, medicine and other relief on the ground say cutbacks have already started, but it will take months or more before the full impact is felt in the poorest countries of Africa, Latin America and Asia.

Aid agencies face more than just the prospect of plummeting donations. The economic conditions themselves - higher food prices and more joblessness - are greatly increasing the number of people who need assistance.

Philippe Guiton of World Vision said that his agency plans to cut back hiring, which will have implications for delivering aid to the needy overseas.

"What we are going to do now is to issue an order to reduce spending, to delay recruitment, delay purchases of capital assets, etc., until we can see clearer how much our income has dropped," he said.

Robert Glasser, secretary-general of CARE International, said the agency has "a number of major donors who have invested heavily in the markets and have now seen their portfolios take a big hit."

What that will mean on the ground could take months or more to gauge - and perhaps years for a complete recovery, aid groups say.