The Guardians Council, which ensures legislation does not violate Iran's constitution and Islamic rules, approved a Tuesday parliamentary vote that endorsed the deal curbing Iran's atomic programme in exchange for an end to sanctions.
The vote came after fierce debate over the terms of the July 14 accord, which has faced a rough ride from hardliners in both Tehran and the US Congress.
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Lawmakers in the United States and Iran, sworn enemies since the Islamic revolution of 1979, had insisted on voting on it.
The deal, which will lift nuclear-related sanctions in return for Tehran, which has always denied seeking an atomic bomb, curbing its nuclear activities.
Members of Congress failed in September to torpedo the deal, with President Barack Obama securing enough support in the Senate to protect the agreement.
Iranian officials have said sanctions should be lifted by the end of the year or January at the latest.
However, Iran also has to satisfy the International Atomic Energy Agency, the UN nuclear watchdog, of the exclusively peaceful nature of its atomic programme.
The IAEA faces a December 15 reporting deadline to resolve what it had termed "ambiguities" over Iran's past nuclear activities.
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