The International Atomic Energy Agency (IAEA) is expected to announce shortly, possibly as early as Friday, that Iran can no longer acquire nuclear weapons as agreed with world powers in July.
"The (European) Council extended until 28 January 2016 the suspension of certain EU restrictive measures against Iran specified in the Joint Plan of Action of November 2013," the EU's foreign affairs service said in a statement.
The EU said that the suspension would allow for "continuous preparations" for the implementation of the July deal and lifting of the sanctions.
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"As soon as the IAEA confirms that Iran has taken the nuclear measures... (the EU) will give effect to the lifting of all EU economic financial sanctions taken in connection with the Iranian nuclear programme, which will supersede the limited sanctions relief extended today."
To get the EU-mediated talks going, the United States, Russia, China, Britain, France plus Germany agreed in November 2013 to suspend some sanctions against Iran as a gesture of goodwill.
The suspension was extended several times during the talks, and then for a further six months after the nuclear deal to give Iran time to meet the conditions.
EU, US and UN sanctions have proved very damaging for Iran, locking up billions of dollars in assets overseas and starving the oil-dependent economy of crucially needed technology and investment.