Mr Zoellick was speaking after a meeting of the main policy making committees of the bank and the International Monetary Fund in Washington.
Mr Zoellick also called on rich nations to do more to help tackle global poverty.
He said the crisis meant targets on tackling poverty in the poorest countries were unlikely to be met.
The World Bank says an extra 53 million people are at risk of extreme poverty.
"There is a widespread recognition that the world faces an unprecedented economic crisis, poor people could suffer the most and that we must continue to act in real time to prevent a human catastrophe," said Mr Zoellick.
He added that no-one yet knew how long the global recession would last.
In a joint statement, the World Bank and the IMF said they had urged "all donors to accelerate delivery of commitments to increase aid, and for us all to consider going beyond existing commitments".