The decision, which eases restrictions on trade in petrochemicals and precious metals and on the provision of insurance for oil shipments, among other measures, was expected to go into effect later in the day.

"This is an important first step, but more work will be needed to fully address the international community's concerns regarding the exclusively peaceful nature of the Iranian nuclear program," the EU's foreign policy chief Catherine Ashton said.

Ashton, who coordinates diplomatic contacts with Iran on behalf of the six powers, said she expected talks on the final settlement to start in February.

The United States and European Union both announced they were suspending some trade restrictions against the OPEC oil producer after the United Nations' nuclear watchdog confirmed that Iran had met its end of the November 24 agreement.

Tehran is expecting to be able to retrieve $4.2 billion in oil revenues frozen overseas and to resume trade in petrochemicals, gold and other precious metals.

Iran and the six major world powers – Russia, China, the US, France, Britain and Germany -- inked a nuclear accord in the Swiss city of Geneva on November 24, 2013. The two sides have agreed to start implementing the agreement from January 20.

Under the Geneva accord, the six countries agreed to lift some of the existing sanctions against Iran in exchange for Tehran’s confidence-building measure to limit certain aspects of its nuclear activities for a six-month period.

NJF/NJF