Read this article: https://inlportal.inl.gov/portal/server.pt/gateway/PTARGS_6_2_3310_277_2....
Liquid flouride thorium reactors are cleaner and safer than uranium reactors. They cannot be used to create nuclear weapons, and instead burn spent uranium fuel, further reducing the availability of fuel that could be used for proliferation.
If the United States government offered to construct one of these safer nuclear reactors, it would provide a cleaner, safer, more sustainable energy source for the country of Iran; would ease fears that Iran is attempting to build a nuclear weapon, and greatly improve the US relations with Iran.