World Bank president Robert Zoellick is warning the world is one shock away from a full-blown crisis.
He cites rising food prices as the main threat to poor nations who risk losing a generation.
Mr Zoellick was speaking in Washington after meetings of the World Bank and the International Monetary Fund.
G20 finance chiefs, who also met in Washington, pledged financial support to help new governments in the Middle East and North Africa.
Mr Zoellick said such support was vital.
He also called for the World Bank to act quickly to support reforms in the region.
''Waiting for the situation to stabilise will mean lost opportunities. In revolutionary moments the status quo is not a winning hand,'' he said.