The International Monetary Fund lowered its 2014 global economic growth forecast, noting "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% for this year, down from its April estimate of 3.7%.
For 2014, the down graded 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 semi annual World Economic Outlook.
The US economy, which accounts for nearly a quarter of the world's gross domestic product, shrunk by 2.9% in the first quarter, in part because of severe winter weather.
Yesterday, the IMF lowered its 2014 US growth forecast to a "disappointing" 1.7%, from 2% in mid-June and 2.8% 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% from 7.6%.
In the euro zone, still struggling to recover from recession, the growth estimate was unchanged at 1.1%, and the IMF reiterated concern about weak inflation in the 18-nation European bloc.