US Secretary of State John Kerry (L) expresses his condolences over the death the of the mother of Iranian President Hassan Rouhani (unseen) before a negotiation session with Iran's Foreign Minister Javad Zarif (R) over Iran's nuclear program in Lausanne March 20, 2015, as European Union Political Director Helga Schmid (4-L) looks on.   Marathon talks towards an Iran nuclear deal picked up pace as US President Barack Obama appealed to Tehran to seize an 'historic' opportunity and begin a 'brighter future'.  AFP PHOTO / POOL /Brian Snyder        (Photo credit should read BRIAN SNYDER/AFP/Getty Images)