Iran has cut higher-enriched uranium stock 'by half'
Iran has neutralised half of its higher-enriched uranium stockpile, as per a deal agreed earlier this year, the world's nuclear watchdog says.
The International Atomic Energy Agency has been checking Iran's adherence to the deal, struck with six world powers.
The US has authorised the release of $450m (£270m) in frozen Iranian funds following the IAEA's latest findings.
Iran agreed to curb its uranium enrichment in return for partial sanctions relief in November.
The six world powers, known as the P5+1, fear Iran's enriched uranium could be used to make a nuclear bomb.
Iran says its nuclear work is peaceful.
Iran has diluted half of its higher-grade enriched uranium stockpile, the IAEA said in a confidential report.
This will be seen as a positive sign by the West as it lengthens the time Iran would need to make a nuclear bomb, says the BBC's Bethany Bell in Vienna.
The US State Department said Washington was releasing the instalment of funds - previously frozen as punishment for Iran's nuclear programme - because "all sides have kept the commitments" they signed up to.
Diplomats confirmed the conclusion of the report with the BBC. The full report is due to be published next week.
The report also said that progress in commissioning a nuclear conversion plant, part of the interim agreement, had been delayed, Reuters reported.
Reduce the scope
The IAEA, which has inspectors in Iran, issues monthly updates on whether Iran is complying with the interim deal with the P5+1.
The temporary agreement came into effect in January, and ends in July.
Iran and the six powers involved - the US, Russia, China, Britain, France and Germany - are keen to start drafting the terms of a new deal by May, but correspondents say they are still some way apart.
The P5+1 wants Iran to agree to permanently reduce the scope of its enrichment programme and to give UN inspectors more oversight.
Iran's Supreme Leader, Ayatollah Ali Khamenei, has backed talks with the P5+1 but warned Tehran will never give up its nuclear programme.
So far, the six world powers have been united in their negotiations but Russia's annexation of the Crimean peninsula from Ukraine last month has caused tension between Moscow and the West.
Russia and Iran are said to be negotiating an oil-for-goods deal thought to be worth up to $20bn (£12bn), which the US says would undermine the nuclear talks.