The world's biggest economies urgently need new ways to support demand and contain risks as the outlook for global growth deteriorates, International Monetary Fund staff members say.

Group of 20 policymakers "must act now to implement forcefully" existing growth strategies while also planning for unified support for demand through fiscal spending, IMF staff said in a report ahead of meeting of finance ministers and central bankers in Shanghai on Friday and Saturday. The IMF is likely to further cut its global-expansion outlook in the next update in April, according to the report.

While officials including U.S. Treasury Secretary Jacob J. Lew have indicated there will not be a massive global effort to stem financial-market turbulence at the G-20, the report builds on calls for greater coordination to support a world economy coping with China's slowdown and falling commodity prices. Staff at the Washington-based lender also called for consideration of an international initiative to support nations at the center of the refugee crisis, saying noneconomic shocks "could have significant spillover impacts."