European bloc says it won't act until IAEA report on nuclear activity, after Tehran says it will breach stockpile limit set in 2015 deal

German Foreign Minister Heiko Maas to visit Tehran, followed by Japanese Prime Minister Shinzo Abe in attempt to dial down tension and salvage nuclear deal

Heiko Maas to visit Tehran next week, meet with counterpart Zarif as Europe looks to salvage 2015 accord

Fearing 'real risk of escalation,' Berlin sends envoy after Iran warns that Germany, France, Britain, China, Russia have 2 months to develop plan to block US sanctions