Iran has previously threatened to break off all cooperation with the u . n . nuclear agency and resume uranium enrichment - the most sensitive phase of the atomic fuel cycle - if the security council steps into the dispute 伊朗先前威胁说，如果安理会介入争端，伊朗就终止与国际原子能机构的所有合作，并恢复浓缩铀提炼。浓缩铀提炼是原子燃料循环中最敏感的阶段。
