WASHINGTON—The global economy risks years of sluggish growth without aggressive steps by central bankers and lawmakers around the world to boost output, the head of the International Monetary Fund said Wednesday.

"The recovery is taking hold, but is too slow," IMF Managing Director Christine Lagarde said in a prepared remarks to Johns Hopkins University's School of Advanced International Studies. The speech set the stage for the spring meeting of finance ministers and central bankers here next week.

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