The board of the international nuclear watchdog has adopted a resolution criticizing Iran's response to the discovery of nuclear substances at undeclared sites in the country.
The resolution, submitted by the United States, Britain, France and Germany, passed on Wednesday at the ongoing board of governors meeting at the headquarters of the International Atomic Energy Agency in Vienna.
Russia and China opposed it.
The IAEA reported in May that Iran failed to provide credible explanations on the nuclear substances.
Iranian media say the country's ambassador to the IAEA denounced the resolution's adoption.
The ambassador hinted at retaliatory measures, saying Iran will take necessary steps, adding that it has the right to review ties with the IAEA.
Negotiations between the US and Iran to revive a 2015 deal on Tehran's nuclear program are stalled. Wednesday's outcome will likely make the negotiations more difficult.