Iran has agreed to give the UN nuclear agency "information and explanations" about "exploding bridge wire detonators" as part of "seven practical measures to be implemented by Iran", the International Atomic Energy Association (IAEA) has said.
The IAEA is currently investigating whether Tehran may have carried out nuclear research and the designing of an atomic bomb.
Iran has rejected any accusation it is working to develop nuclear weapons, agreeing to cooperate with IAEA to clear any "ambiguities".
Iran will begin to freeze part of its nuclear programme in return for the sanctions relief from January 20.
The deal, agreed between Iran and world powers after months of negotiation led by the EU's foreign policy chief Catherine Ashton, is hinged on Iran curbing its enrichment of uranium.
Officials have another six months from January 20 to agree a final settlement about the activity the West suspects is aimed at obtaining nuclear weapons capability.
William Hague has hailed implementation of an interim deal to freeze Iran's nuclear programme.The Foreign Secretary said the agreement coming into force was an "important step" in settling the differences between the Middle East and international powers.
The United States said that although sanction relief will begin immediately the full benefits will not be released until the deal reaches its end.
Iran will start to receive sanction relief from the first day of the interim nuclear deal, 20th January a US official has confirmed.
Once the IAEA confirms that Iran has implemented the deal on 20th January, the US will suspend some petrochemical and precious metal sanctions.
An interim nuclear deal between Iran and six world powers and Iran will start on 20th January, the EU's foreign policy chief Catherine Ashton said.
Ashton represents the six nations - the United States, Russia, China, France, Britain and Germany - in diplomatic contacts with Iran related to the nuclear standoff.
She said the sides would now ask the United Nations' nuclear watchdog to verify the deal's implementation.
"We will ask the IAEA to undertake the necessary nuclear-related monitoring and verification activities," she said.
Under the agreement, Iran has promised to curb its most sensitive nuclear activities in return for some relief from Western economic sanctions.
The IAEA report said that "extensive activities" at the Parchin military compound - an allusion to suspected Iranian attempts to remove evidence - would seriously undermine an agency investigation into indications that research relevant to developing a nuclear explosive were conducted there.
The IAEA delivered its latest quarterly Iran report 10 days after U.S. President Barack Obama's re-election raised hopes of a revival of nuclear diplomacy with Iran following speculation that Israel might bomb Iranian nuclear facilities.
Iran denies aiming to acquire nuclear weapons, saying its atomic programme is solely for peaceful energy purposes.
Iran is ready to sharply expand its uranium enrichment in an underground site after installing all the centrifuges it was built for, a U.N. nuclear report showed, a development likely to fuel Western alarm over Tehran's nuclear aims.
The Islamic state has put in place nearly 2,800 centrifuges that the Fordow enrichment site, buried deep inside a mountain, was designed for and could soon double the number of them operating to almost 1,400, according to an International Atomic Energy Agency report obtained by Reuters.
Israel is facing growing international pressure not to attack Iran unilaterally, with the US in particular making clear its firm opposition to any such strike. It follows pressure on world leaders to halt Iran's contested nuclear programme.
The US Chairman of the Joint Chiefs of Staff General Martin Dempsey made comments that Washington did not want to be blamed for any Israeli initiative, according to an interview with the Guardian.
A report by the UN's nuclear watchdog that accused Iran of doubling the number of uranium enrichment entrifuges it has in an underground bunker was politically motivated, as Iranian lawmaker said today.
The International Atomic Energy Agency (IAEA) report yesterday indicated that despite threat of an Israeli or US military strike on Tehran's nuclear facilities, it was rapidly increasing the enrichment capacity of its Fordow site, buried deep underground to withstand any such hit.
"Publishing this report while Iran is holding the Non-Aligned Movement (NAM) meeting does not mean anything other than it was a political move aimed at overshadowing the meeting in Tehran," lawmaker Kazem Jalali told the ISNA news agency.