The 193 member countries of the United Nations have agreed to cut the UN's budget for only the second time in the past 50 years.
After a series of all-night negotiations, the 2012-13 budget has been set at $US5.15 billion, down from $US5.41 billion in 2010-11.
The United States and European countries had fought for cuts while developing countries had demanded spending be kept up.
UN Secretary-General Ban Ki-moon says there will be more cuts in coming months, because he says the UN has to cut fat.
"Governments and people everywhere are struggling," he said.
US negotiator Joseph Torsella called the budget a "historic agreement" though he acknowledged it had taken difficult negotiations.
This accord "is the first time since 1998 - and only the second time in the last 50 years - that the UN regular budget has declined in comparison to the previous budget's actual expenses," he said
Mr Torsella called it a "budget for a strengthened, more efficient, and more effective United Nations that saves the American taxpayers millions of dollars and sets the United Nations on the path of real fiscal discipline and continued reform".
The United Nations has already cut posts and contracted out services in many departments at the New York headquarters.
Several of the UN's foreign missions saw their budget cut, including in Ivory Coast where UN peacekeepers fought followers of incumbent Laurent Gbagbo after he refused to stand down after losing an election.