Iran nuclear deal 'based on proof not trust', says Kerry
An outline agreement on the future shape of Iran's nuclear programme has been reached after marathon talks with six major powers in Switzerland.
Under the deal, Iran will reduce its uranium enrichment capacity in exchange for phased sanctions relief.
US President Barack Obama said a "historic understanding" had been reached with Iran.
Speaking to the BBC's Barbara Plett Usher, US Foreign Secretary John Kerry described the agreement as being, "based on proof, not trust".