Iranian scientists have run computer simulations for a nuclear weapon that would produce more than triple the explosive force of the World War II bomb that destroyed Hiroshima, according to a diagram obtained by The Associated Press.

The diagram was leaked by officials from a country critical of Iran’s atomic program to bolster their arguments that Iran’s nuclear program must be halted before it produces a weapon. The officials provided the diagram only on condition that they and their country not be named.

The International Atomic Energy Agency — the Vienna-based U.N. nuclear watchdog — reported last year that it had obtained diagrams indicating that Iran was calculating the “nuclear explosive yield” of potential weapons. A senior diplomat who is considered neutral on the issue confirmed that the graph obtained by the AP was indeed one of those cited by the IAEA in that report. He spoke only on condition of anonymity because he was not authorized to discuss the issue.