REUTERS/Herwig Prammer

Iran’s ambassador to the International Atomic Energy Agency Ali Asghar Soltanieh briefs the media during a board of governors meeting at the United Nations headquarters in Vienna March 8. Six world powers demanded Thursday that Iran fulfill a promise to let international inspectors visit a military installation where the UN nuclear watchdog believes that explosives tests geared to developing atomic bombs may have taken place.

Has Iran already secretly tested a small nuclear warhead or dirty nuclear bomb in North Korea?

The question is the latest plot twist in a growing international debate between the United States and Israel over whether or not to launch preemptive military attacks on Iran’s suspected nuclear weapons program.

Last week, while U.S. President Barack Obama and Israeli Prime Minister Benjamin Netanyahu were meeting in the White House and disagreed over the threat posed by Iran, scientists and security officials around the world were debating whether North Korea may already have served as a secret nuclear testing ground for Iran.

A February report in the science magazine Nature opened the door to that possibility, when it reported on a soon-to-be-published Swedish scientific study that concludes North Korea conducted two secret, small-scale, nuclear tests in mid-April and mid-May 2010.

The magazine said Dr. Lars-Erik De Geer, an atmospheric scientist with the Swedish Defence Research Agency in Stockholm, began investigating bizarre claims North Korea made in May 2010 that it had successfully achieved nuclear fusion.

The North Korean claims were generally ridiculed and dismissed by experts, but South Korean scientists said they did detect a whiff of the radioactive gas xenon at the time.

Dr. De Geer decided to follow up the reports and spent a year studying radioisotope data gathered from monitoring stations in South Korea, Russia and Japan, as well as reviewing South Korean meteorological records.