International Atomic Energy Agency chief Yukiya Amano met with the envoys of the three countries on the sidelines of the agency’s week-long board meeting here, where Washington, Paris and Moscow formally handed over their responses, a diplomat close to the IAEA said, speaking on condition of anonymity.

The move comes just hours ahead of a key vote by the UN Security Council in New York which was expected to slap a fourth set of sanctions on the Islamic republic over its contested nuclear programme.

Amano has been waiting for the three powers’ views on a deal drawn up by Iran, Brazil and Turkey on May 24 regarding the supply of fuel for a nuclear research reactor in Tehran.

The three — known as the so-called Vienna group — had originally proposed last October that they take most of Iran’s stockpile of low-enriched uranium (LEU) and turn it into the much-needed fuel for the reactor which makes radioisotopes for medical use.

But Iran refused to take up the offer and has drawn up an alternative deal with Brazil and Turkey instead.

The diplomats said they had not yet seen the contents of the letter.

But the West has cold-shouldered Iran’s proposal, saying it did not go far enough to allay fears that Tehran is using its contested nuclear drive as a mask for a covert atomic weapons programme.