Mr Hague said the latest report from the International Atomic Energy Agency "provides further evidence" of why the international community should be concerned about Iran's nuclear programme.

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Iran, which is subject to an array of international sanctions, has long argued that its nuclear programme is for energy generation and research.

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Speaking to the Today programme, Phil Bentley said that volatility on the international energy markets meant price rises had had to be made, and the trend would continue unless a new source of cheap gas was discovered.

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Iran insists its nuclear programme is peaceful, but the UN's International Atomic Energy Agency says it has information suggesting Iran has carried out tests "relevant to the development of a nuclear explosive device".

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They also point out that the International Atomic Energy Agency (IAEA) would have to certify that Iran's nuclear programme is entirely peaceful, which it has so far been unable to do.

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French energy company Total says it has stopped petrol deliveries to Iran, amid growing international pressure over Iran's nuclear programme.

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Any deal would need to constrain Iran's uranium enrichment and subject it to enhanced verification by the International Atomic Energy Agency, the UN's nuclear watchdog, all the while helping to advance those bits of the programme that are demonstrably non-military in character.

ECONOMIST: Iran