Amid mounting Gulf tensions, Tehran set to announce resumption of ‘limitless’ uranium enrichment at shuttered Arak heavy water reactor

Official from country's atomic agency says move part of 60-day ultimatum laid down by President Rouhani for negotiating new terms

Spokesman for country's atomic agency insists actions ordered by President Rouhani in response to US sanctions do not violate 2015 agreement

Spokesperson says Tehran is eager to see landmark 2015 pact strengthened, as Europe says it won't cave to regime's 'ultimatums'