The U.S. should grow by 2.8% this year, up from 1.9% in 2013, as strengthening domestic demand gets a boost from smaller spending cuts as a result of the recent budget deal.
Recovery from recession in the eurozone will remain uneven, the IMF said, raising its forecasts for growth in Germany and Spain, but trimming Italy and leaving France unchanged.
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The European Central Bank cut interest rates in November after inflation sank to 0.7%. ECB President Mario Draghi said earlier this month that he's ready to use all the tools at the bank's disposal should prices take another turn lower.
The biggest upgrade to the IMF's October forecast was for the U.K., where cheap central bank money has helped drive a sharp recovery in consumer and business confidence.
Japan will also do better than expected, with growth seen broadly unchanged at 1.7% as a temporary fiscal stimulus package offsets the impact of a rise in consumption tax.
Emerging markets should grow on average by just over 5% in 2014, up from 4.7% last year. But the headline forecast is unchanged since October and reflects a mixed picture.