Section 123 of the United States Atomic Energy Act of 1954, titled "Cooperation With Other Nations", establishes an agreement for cooperation as a prerequisite for nuclear deals between the US and any other nation. Such an agreement is called a 123 Agreement. To date, the U.S. has entered into roughly twenty-five 123 Agreements with various countries.

Countries with which the U.S. has or had a 123 Agreement:

* Morocco
* Ukraine
* Romania
* Japan (with automatic re-processing rights)
* Euratom (with automatic re-processing rights)
* China (with re-processing rights, requiring approval per each request)
* Switzerland
* India (draft completed, requires signatures from U.S. and India - the agreement is witnessing opposition within India from parties of the Left Front)
* (other countries - to do)