UN secretary-general Ban Ki Moon warned on Thurday that a drop in international aid to developing countries - the first in years - will scupper efforts to reduce poverty by 2015.
He spoke at the launch of a new report into the the Millennium Development Goals' progress which shows that official aid fell to $133 billion (£80bn) in 2011.
That's less than half the $300bn (£185bn) needed each year to meet the goals set by world leaders in 2000.
Mr Ban urged donor countries to step up and plug the gap.
"Do not place the burden of fiscal austerity on the backs of the poor - either in your own countries or abroad," he said.
The report shows that 16 big donors gave out less cash, mainly in response to the global economic crisis.
Mr Ban warned that essential medicines are too expensive and only half of public health facilities in developing countries are able to provide them.
The millennium goals include cutting extreme poverty by half, ensuring that every child has a primary school education, halting and reversing the HIV-Aids pandemic, reducing by half the number of people without access to clean water and basic sanitation, cutting child mortality by two-thirds and maternal mortality by three-quarters.