William Hague has hailed the implementation of an interim deal to freeze Iran's nuclear programme.
The Foreign Secretary said the agreement coming into force next Monday was an "important step" in settling the differences with international powers.
The deal, hammered out in November, will see Iran halt enrichment of uranium above 5% purity, "neutralise" its stockpile of 20% enriched uranium and provide daily access to inspectors.
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In return, the E3+3 nations - US, Russia, China, Britain, France and Germany - will ease some trade sanctions such as in petrochemicals and gold.
Mr Hague said: "I welcome the fact that we have now reached E3+3 agreement with Iran on implementing the first step of the Joint Plan of Action agreed at Geneva on November 24, 2013."