The International Monetary Fund is projecting a modest uptick in global economic growth for 2013. But an IMF report released Wednesday also warns that problems in the eurozone and the United States could derail momentum.

The report was an update of the fund's World Economic Outlook. It was largely consistent with the original report's estimate in October, revising global growth down slightly by a tenth of a percentage point to 3.5 percent. The world economy grew 3.2 percent in 2012, according to IMF estimates.

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 how the crisis would be resolved is weighing down growth prospects. The IMF warned that the eurozone "continues to pose a large downside risk to the global outlook."

The new report was more optimistic about the U.S. economy. It forecasts 2 percent growth for 2013, but said 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 cuts and a dispute between President Barack Obama and lawmakers over its borrowing authority.

The IMF warned that the U.S. should avoid sharp cuts in the short term, but improve its books over the medium term by cutting social programs and passing tax reforms.

The updated report projected that stimulus policies in Japan would pull the country out of a brief recession. But it warned that the country had to deal with its debt in the medium term.

The IMF also noted that growth in developing economies could be hurt by the problems still facing the U.S., Europe and Japan.