Head of the country's atomic energy agency says Iran will stay below 20% threshold; announcement comes as Tehran says it will restart centrifuges at underground Fordo plant

Both Brussels and Moscow urge return to collapsing nuclear accord, though Putin's office says it understand's Tehran's position

Where the accord now stands, with Tehran taking another step away from the 2015 agreements to curb its nuclear development

President Rouhani says uranium gas to be injected into 1,044 centrifuges at underground nuclear site

MP Akbar Torki says Gulf state has 'understood that Western countries and Saudi Arabia cannot provide the country with security'

Lack of American response to crippling attack on oil facilities has shown Riyadh that Washington 'not really ready to take on Iran,' analyst says

US president confirms Washington, Tehran officials considered a meeting in New York last week, says he balked when Iranian president demanded sanctions relief first

Russian leader says US has not produced proof of Tehran's link to September strikes that rattled global energy markets

Iranian president says he was willing to accept European framework that included lifting sanctions, but then US leader publicly declared he would increase them

Paris officials say proposal would have seen Washington roll back all re-imposed sanctions and Tehran recommit to 2015 accord