Diplomats say Russia, backed by China, has refused to approve a report saying Iranian missile tests a year ago violated United Nations sanctions.
The block effectively rules out any expansion of UN sanctions against Iran, at least for now.
Australia's UN ambassador, Gary Quinlan, who chairs the committee monitoring sanctions on Iran, said on July 15 that the Security Council also declined to endorse the committee's conclusion that Iran probably violated sanctions by shipping weapons to Yemeni insurgents.
The arms were intercepted by Yemeni forces in January.
Russia's deputy ambassador to the UN, Pyotr Ilyichov, said Russia opposes further sanctions and does not see an alternative to a diplomatic settlement of the standoff over Iran’s nuclear and missile programs.
The Islamic republic denies allegations it is seeking to develop nuclear weapons.
Based on reporting by AP, Reuters, and ITAR-TASS