World Bank president Robert Zoellick says 2009 is shaping up to be a "very dangerous year" for the global economy.
He believes the economic outlook is worse than the International Monetary Fund's prediction of growth of 0.5% this year.
He was speaking ahead of Saturday's G20 finance ministers meeting in Britain on how best to tackle the worst economic slowdown in decades.
Mr Zoellick said it will be a positive sign if the G20 supports extended International Monetary Fund resources, condemns protectionism and supports practical solutions.
The G20 includes the Group of Seven industrialised countries - Britain, Canada, France, Germany, Italy, Japan and the United States - the European Union and leading developing nations including Brazil, China and India.
Finance ministers and central bank leaders from the United States and Europe go into Saturday's meeting deeply divided on whether stimulus packages or tighter regulation of the finance sector should be the way forward.
The gathering in Horsham, near London, is expected to lay the groundwork for a G20 heads of state summit on 2 April.