The vote reflected congressional criticism of the U.N. following allegations of corruption and mismanagement in the oil-for-food program for Iraq, sexual abuses by peacekeepers, and other scandals.
U.S. dues are now capped at 27.1 percent of the peacekeeping budget. Under a 1994 law, that cap is to be reduced to 25 percent.
The United States is expected to spend about $1 billion on peacekeeping operations this year, with much of the money for activities in Sudan and Haiti. The Bush administration is seeking about the same amount for next year.