Foreign Secretary William Hague said Iran should "be more realistic about what is necessary" to reach a nuclear deal with major powers.
Hague made the comments shortly after a meeting with US Secretary of State John Kerry in Vienna.
They were joined in the Austrian city by their French and German counterparts for talks about Iran's nuclear programme.
Six months ago, a deadline to reach an agreement was set for July 20.
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Ukip leader Paul Nuttall also said he would want to get rid of Sharia courts.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.
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