Among the challenges are rising oil prices, unrest in the Middle East, continued inflation in China and debt problems in Europe.
In a newforecast, the IMF says the global economy should grow by 4.4% in 2011, the same figure given in January.
But the IMF cut its UK growth forecast for 2011 to 1.7% from 2%.
It kept its predictionfor UK economic growth in 2012 unchanged at 2.3%.
Meanwhile, it raised its forecast for Germany's GDP growth this year to 2.5% from 2.2%, and its forecast for 2012 rose slightly to 2.1%.
On the global economy the IMF said: "The recovery has solidified, but unemployment remains high."
In its World Economic Outlook report the IMF also said that growth was not strong enoughto make a "major dent in high unemployment rates".
And it said that the major risk to growth came from further oil price rises because of supply disruption.
It said the eurozone economy wasexpected to grow by 1.6% in 2011 and 1.8% the following year, a 0.1 percentage point increase on its January forecast.
It painted a gloomy picture for Portugal's economy, saying it would stay inrecession during 2012, with the unemployment rate expected to rise from its current 11.1% to 12.4% by 2012.
Greece and the Irish Republic also faced tricky financial readjustments, it said.
MeanwhileSpain, which has unveiled spending cuts to try to stave off any potential bail-out, will record growth of 0.8% this year and 1.6% in 2012, the IMF said.
Growth in the US waspredicted to be 2.8%, down 0.2 percentage points from January, reflecting the effect of higher oil prices.
And the IMF warned about inflation building in Asia's fast-growing economies, cautioning that"boom-like dynamics" should not be allowed to get out of control.
The Washington-based body said if China were to suffer a slowdown - after a credit and property-fuelled boom - it would hurt the...