Six countries, including the US and the UK, are to recommence multi-lateral talks with Iran over its suspected nuclear weapons programme, the EU has said.
The move comes on the same day that Iranian diplomats said UN inspectors could visit the disputed Parchin facility, where it is claimed the country is researching nuclear explosives.
Iran's nuclear negotiator Saeed Jalili proposed the new talks with the US, UK, France, Germany, China and Russia in February. In agreeing to the discussions, EU foreign policy chief Catherine Aston said it was time for "real progress".
Ashton said she hoped Iran "will now enter into a sustained process of constructive dialogue which will deliver real progress in resolving the international community’s long-standing concerns on its nuclear program".
Following Baroness Ashton’s announcement the UK, US, France, Germany, Russia and China all agreed to take part in the talks.
Foreign Secretary William Hague said: "We all agree that the international community should demonstrate its commitment to a diplomatic solution by acknowledging Iran’s agreement to meet, by testing its desire to talk and by offering it the opportunity to respond to our legitimate concerns about its nuclear intentions.
"It is time for Iran to choose a different path and to show the world that it wants a peaceful, negotiated solution to the nuclear issue. It is for Iran to seize this opportunity and we urge it to do so.
“The onus will be on Iran to convince the international community that its nuclear programme is exclusively peaceful, by taking concrete actions."
Tenions have been raised with Iran in recent weeks over the West's fear that Tehran is closer than ever to developing a nuclear arsenal.
EU sanctions set to come into force in July include bans on Iranian oil exports. Iran has already responded to the ban by threatening its own embargo on selling crude oil to some EU nations, including France and the UK.
Earlier, the Cabinet was briefed on Iran's nuclear programme. National Security Adviser Sir Kim Darroch led the presentation, which also featured "a number of experts", the Prime Minister's official spokesman said.
The discussion - which lasted around an hour - came after US President Barack Obama held talks with Israeli Prime Minister Benjamin Netanyahu in Washington to discuss the issue on Monday.
The Israelis have shown increasing signs of impatience that diplomatic pressure has so far failed to persuade Tehran to abandon the programme, prompting speculation they could mount air strikes.
No. 10, however, stressed that Britain remained committed to pursuing a diplomatic solution to the issue.
"We believe that that strategy of continuing to apply pressure on the regime is the right one," the PM's spokesman said.
"Clearly our objective here is to see Iran change course and engage with the international community. We believe sanctions are having some effect."
David Cameron is due to answer detailed questions on Iran when he appears before MPs on the Commons liaison committee on Tuesday.
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