The United States and Europe have begun preparing to lift the trade sanctions that have hobbled the Iranian economy, as a historic nuclear deal comes into effect.
The procedure to lift the embargo began 90 days after the UN Security Council endorsed the accord signed in Vienna in July, a milestone referred to as ''Adoption Day.''
But foreign firms will not be able to resume ties with Iran's oil industry and banks right away - sanctions will remain in place until Iran fulfils its end of the bargain.
The next stage in the process - ''implementation day'' - will only come when the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, confirms Iran has dramatically scaled back its nuclear programme.
Iran said that lengthy process will probably start this week.
Envoys of the deal signatories - Britain, China, France, Germany, Russia and the United States - will meet today in Vienna to form a commission to oversee the implementation of the accord.
Tehran will have to surrender or dilute the bulk of its enriched nuclear fuel stocks, dismantle most of its centrifuges and halt a reactor capable of making plutonium.
Only then will the sanctions ''waivers'' that US President Barack Obama ordered his administration to issue on Sunday come into effect and trade can begin to resume.
''Today marks an important milestone toward preventing Iran from obtaining a nuclear weapon and ensuring its nuclear program is exclusively peaceful going forward,'' Obama said in a statement.
US Secretary of State John Kerry, who played a central role in the painstaking negotiations between Iran and the West, added, ''If fully implemented, it will bring unprecedented insight and accountability to Iran's nuclear program forever.''
The European Union also adopted a legal framework for lifting sanctions imposed on Iran.
The accord ''brings us a step closer to the beginning of implementation of the (July deal), to which we are strongly committed,'' EU foreign policy chief Federica Mogherini said in a joint statement with Iranian Foreign Minister Javad Zarif.
US Treasury Secretary Jacob Lew said, ''As Iran begins taking its nuclear-related measures and the United States and our partners prepare to lift nuclear-related sanctions in response, we move one step closer to a successful JCPOA and a more secure international community,'' using the acronym for the nuclear accord.
(Also see: Post-sanctions Iran banking hugely on tourist industry)