European Union foreign policy chief Catherine Ashton wrote to Iran's chief nuclear negotiator on Tuesday, accepting an offer to meet to discuss Tehran's nuclear programme.
Ashton represents six powers - the United States, Russia, China, France, Britain and Germany - in dealings with Iran, and her offer of talks came after weeks of consultations with them.
It follows the expansion of sanctions by Europe and the United States to exert economic pressure and force Tehran to hold back on its nuclear programme, which they fear aims to produce atomic weapons. Iran says it is enriching uranium for peaceful purposes only.
In a letter last month, Iran's chief nuclear negotiator, Saeed Jalili, proposed that negotiations with global powers should resume after more than a year's standstill, and said Tehran would have new initiatives to bring to the table.
Today I have replied to Dr Jalili's letter of February 14, Ashton said in a statement. I have offered to resume talks with Iran on the nuclear issue, she said.
Ashton's letter proposed an initial round of talks to focus on building confidence by developing concrete steps for the future.
Our overall goal remains a comprehensive negotiated, long-term solution which restores international confidence in the exclusively peaceful nature of Iran's nuclear programme, while respecting Iran's right to the peaceful use of nuclear energy, she said in her reply to Jalili.
Ashton said the time and venue for talks should now be decided but noted she wanted talks to resume as soon as possible.
In practical terms, she wrote, our deputies could get together in the near future in order to prepare for the first round of our resumed talks.
In another possible step towards greater cooperation, Iran said on Tuesday it would let U.N. nuclear investigators visit a military complex where they had been refused access, to check intelligence suggesting Tehran has pursued explosives research relevant to nuclear weapons.
Western states are likely to tread cautiously, mindful of past accusations that Iran's willingness to talk has been a tool to buy time and not a path to agreement.
Officials say Iran faces an unprecedented strain on its economy due to the expansion of sanctions on its oil and financial sectors. In July, an EU embargo on Iranian crude is due to take full effect, drastically shrinking its export markets.
(Editing by Ben Harding)