Inflation risks and global trade imbalances mean the world economy faces "testing times", the head of the International Monetary Fund (IMF) said.
The IMF chief sees no quick fix to solving global trade imbalances
Deadlocked trade talks are another challenge Rodrigo de Rato added, ahead of a series of IMF and World Bank meetings in Singapore.
World Bank head Paul Wolfowitz, meanwhile, has branded Singapore as "authoritarian" for banning protestors.
More than 160 groups have boycotted the talks over the move.
They include leading non-governmental organisations who were accredited for the talks, including Friends of the Earth.
The Asian city state banned 28 civil rights activists from entering the country and deported other would-be attendees.
Hundreds of activists have gathered on the nearby Indonesian island of Batam in response to restrictions on protests.
"The protest represents both the fact that people were barred from coming in to Singapore, and also the fact that poor countries don't have a strong enough voice in the bank and the fund," said Taylor Thompson, a spokeswoman for Global Call To Action Against Poverty, a coalition of groups.
ActionAid joined in the protests, saying the World Bank and IMF should never again "hold their annual meetings in countries restricting civil and political liberties".
Its comments came after four ActionAid members of staff were detained at Singapore's Changi airport.
"Enormous damage has been done and a lot of that damage is done to Singapore and is self-inflicted," Mr Wolfowitz said.
Separately, Mr Wolfowitz reiterated that misuse of funds the organisation lent to tackle poverty could not be tolerated.
"If we're going to get out of poverty, the money has to go where its supposed to go and not line the bank accounts of government officials," he said.
In its World Economic Outlook published earlier this week, the IMF predicted the global economy would grow 5.1% this year then 4.9% in 2007.
However, it forecast the US would see growth slow to 2.9% next year from 3.4% in 2006.
Mr de Rato said that global trade imbalances, seen especially in China's trade surplus and the US budget deficit, were "complex problems that took many years to build up".
"It would be unrealistic to expect the problem to be resolved through a quick fix", he said.
Mr de Rato added that the world economy had shown resilience in the face of higher oil prices and rising interest rates.