Iranian President Hassan Rouhani said a nuclear deal sealed with world powers on Tuesday will open "new horizons" now that "this unnecessary crisis" has been resolved.
In a message on his Twitter account, Rouhani said the successful talks had shown "constructive engagement works."
There can now be "a focus on shared challenges", he added, alluding to Sunni Muslim extremists of the Islamic State group, who from their base in Iraq and Syria are launching attacks on both Shiite and Western targets worldwide.
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Rouhani's tweet came shortly after Iranian Foreign Minister Mohammad Javad Zarif announced at talks in Vienna: "We are starting a new chapter of hope."
Since his election in 2013, Rouhani has sought to end the 13-year-old standoff with Western governments over Iran's controversial nuclear programme -- and with it the sanctions that have paralysed Iran's economy.
Iran has always denied Western suspicions that it has been trying to acquire the know-how to make an atomic bomb.
Rouhani's message echoed an English language YouTube video on July 3 in which Zarif said a nuclear accord could "open new horizons to address important common challenges", referring to the "growing menace of violent extremism and outright barbarism," an implicit reference to IS.