The major step is the culmination of several festering stand-offs between the International Atomic Energy Agency and Iran.

The International Atomic Energy Agency's findings could lead to further tensions and set in motion an effort to restore United Nations sanctions on Tehran later this year.

The UN nuclear watchdog's 35-nation board of governors passed a resolution on Thursday formally declaring Iran in breach of its non-proliferation obligations for the first time in almost 20 years, with Tehran responding that it would open a new uranium enrichment site.