The United States and Argentina have collaborated for years to eliminate Argentina's stocks of highly enriched uranium (HEU). Since this cooperative effort began, over 40 kilograms of HEU have been removed from Argentina. Before the 2016 Nuclear Security Summit, approximately 4 kilograms of HEU remained that was not eligible to be returned to the United States because of its form and composition. Argentina was able to eliminate all of its HEU because it converted its medical isotope production to the use of low-enriched uranium (LEU) targets in 2002 and converted its last reactor from HEU to LEU fuel in 2008.
At the 2016 Summit, Argentina announced the successful disposition of Argentina's remaining HEU. The U.S. Department of Energy and Argentina's National Atomic Energy Commission cooperated to down-blend and dispose this material in Argentina.
Having completed this down-blending project, Argentina — and the entire Latin America and Caribbean region — is now considered free of HEU, which is understood to mean that no country has more than 1 kilogram of HEU.
Barack Obama, Fact Sheet: Eliminating All Highly Enriched Uranium from Argentina Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/318387