"Iran has taken every step that it committed to take, dating back two full years," US Secretary of State John Kerry said in Vienna as International Atomic Energy Agency (IAEA) certified that Iran has fulfilled its promises.
The US sanctions-related commitments are now in effect, Kerry said, announcing lifting of sanctions against Iran.
The landmark deal between Iran and world powers - the US, UK, Russia, China, France and Germany - was agreed last July.
"This achievement clearly demonstrates that with political will, perseverance, and through multilateral diplomacy, we can solve the most difficult issues," she said.
More From This Section
Lifting the sanctions will unfreeze billions of dollars of assets, allow Iran's oil to be sold internationally and reconnect Iranian banks to the global system.
In its report, IAEA said Iran has shipped 98 per cent of its fuel to Russia and dismantled more than 12,000 centrifuges so that they could not enrich uranium any further.
Kerry also said the international community can now finally work to address the other regional challenges without the looming threat of a nuclear-armed Iran - including the Syrian crisis, on which important progress in recent months have been made.
Hours later in Washington, the US State Department announced lifting of sanctions on Iran and the White House said President Barack Obama signed an executive order lifting some of the US economic sanctions on Iran.
The announcement also followed news of a prisoner swap between Iran and the US. Iran released four American prisoners including a The Washington Post correspondent.