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

Iran warned it will retaliate following a decision by the United Nations atomic watchdog to censure the Islamic Republic over its nuclear program, deepening a crisis that’s also drawn in the US and Israel.

Western nations are planning to table a resolution at an IAEA meeting that will find Iran in non-compliance with its so-called safeguards obligations for the first time in 20 years, a senior western diplomat said.