IMF sees modest 2013 improvement for world economy

The report Wednesday, an update of the fund's World Economic Outlook, largely tracked the initial estimate from October, revising global growth down slightly by one-tenth of a percentage point, to 3.5 percent. The world economy grew 3.2 percent in 2012, according to IMF estimates.

"Some cautious optimism may indeed be justified," said the IMF's chief economist, Olivier Blanchard. "But we should be under no illusions: there remain considerable challenges ahead."

The IMF downgraded its forecast for the 17-country eurozone, projecting a slight economic contraction for 2013. It said that despite positive policy steps to tackle the debt crisis in some eurozone countries, continued uncertainty about a resolution to the crisis is weighing down growth prospects.

The IMF warned that the eurozone "continues to pose a large downside risk to the global outlook."

The revised report was more optimistic about the U.S. economy, forecast to grow by 2 percent for 2013. But prospects could change depending on impending tax and spending decisions. The U.S. government faces a series of budget negotiations as it tries to navigate mandated spending cuts and a dispute between President Barack Obama and lawmakers over the country's borrowing authority.