Nikki Haley, who is chairing the council this month, said Iran and Lebanon's Hizballah have trained 'deadly militias' that they use to fuel conflicts in Syria, Iraq, and Yemen.
'For decades, they have committed terrorist acts across the region,' Haley said.
'Iran is using Hizballah to advance its regional aspirations,' she said. 'They are working together to expand extremist ideologies in the Middle East. This is a threat that should be dominating our discussion' at the UN.
Iranian Ambassador Gholamali Khoshroo fired back, calling the allegations 'unsubstantiated' and saying the United States only raised the issue 'to remove the Palestinian issue that is central to all the conflicts in the Middle East from these open debates.'
Russia's deputy UN ambassador Petr Iliichev also defended Iran, questioning why Haley did not mention threats from the Islamic State and Al-Qaeda allies in Syria and Iraq, where they have been battling Iranian-backed militias allied with the governments.
'We're invited to consider as terrorists those who are fighting these groups,' he said.
Based on reporting by AP and AFP