From the Document: "The IAEA [International Atomic Energy Agency], an autonomous intergovernmental organization related to the United Nations, has 171 member states, including the United States. Its missions include promoting nuclear power, nuclear safety, nuclear security, and nuclear technology for medical and agricultural purposes, as well as implementing safeguards in more than 180 countries. A country does not have to be a member in order to have inspections or receive IAEA technical assistance. The Nuclear Nonproliferation Treaty (NPT) requires non-nuclear-weapon states parties to forego developing or otherwise obtaining nuclear weapons. To ensure compliance with this requirement, the treaty also requires these states to conclude comprehensive IAEA safeguards agreements. Such agreements are designed to enable the IAEA to detect the diversion of nuclear material from peaceful purposes to nuclear weapons uses, as well as to detect undeclared nuclear activities and material. [...] The United States is the largest contributor to the IAEA, providing an estimated $200 million annually in assessed and voluntary contributions. The share of U.S. contributions is typically about 25% of the regular IAEA budget, as is the case for FY2020, but can fluctuate slightly from year to year, depending on such factors as the total budget and number of members that are assessed."
CRS Report for Congress, R44384
Congressional Research Service: https://crsreports.congress.gov/