The International Monetary Fund lowered its 2014 global economic growth forecast Thursday, warning of "negative surprises" from the United States and China and geopolitical risks in Ukraine and the Middle East.
The IMF projected global growth of 3.4 percent for this year, down from its April estimate of 3.7 percent.
The world's economy is likely to pick up steam in 2015, with growth at an annual rate of 4.0 percent, the global lender said.
For 2014, the downgraded growth outlook reflects "both the legacy of the weak first quarter, particularly in the United States, and a less optimistic outlook for several emerging markets," the IMF said, in an update of its semiannual World Economic Outlook.
The US economy, which accounts for nearly a quarter of the world's gross domestic product, shrunk by 2.9 percent in the first quarter, in part because of severe winter weather.
On Wednesday, the IMF lowered its 2014 US growth forecast to a "disappointing" 1.7 percent, from 2.0 percent in mid-June and  2.8 percent in April.
"It's really a story of something which has just happened and that is behind us," said Olivier Blanchard, the IMF's chief economist.
For China, the world's second-largest economy, output this year will expand less than previously thought, the IMF said, lowering its forecast to 7.4 percent from 7.6 percent.
In the eurozone, still struggling to recover from recession, the growth estimate was unchanged at 1.1 percent, and the IMF reiterated concern about weak inflation in the 18-nation European bloc.