United Nations Issues: U.S. Funding of U.N. Peacekeeping [Updated August 14, 2019] [open pdf - 437KB]
From the Document: "The United States is the single largest financial contributor to U.N. peacekeeping activities. Congress authorizes and appropriates U.S. contributions, and it has an ongoing interest in ensuring such funding is used as efficiently and effectively as possible. The United States, as a permanent member of the U.N. Security Council, plays a key role in establishing, renewing, and funding U.N. peacekeeping operations. For 2019, the United Nations assessed the United States share of U.N. peacekeeping operation budgets at 27.89%; however, since 1994 Congress has capped the U.S. payment at 25% due to concerns that the current assessment is too high. For FY2019, total enacted U.S. funding for U.N. peacekeeping is $1.65 billion."
CRS In Focus, IF10597
Congressional Research Service: https://crsreports.congress.gov/