Rouhani spoke minutes after US President Barack Obama’s comments on the agreement struck in Vienna were also broadcast live on state television.
But Obama’s speech was cut off when Rouhani, who has staked his presidency on resolving the nuclear standoff with the West, took to the podium to address the nation.
“If this deal is implemented correctly… we can gradually eliminate distrust,” he said, alluding to Iran’s long-strained relations with leading Western states.
“This is a mutual deal, a reciprocal deal,” he added, noting that “all our objectives” had been met under the final deal as sanctions would be lifted and a civilian nuclear programme acknowledged.
The deal would “take the nuclear dossier” out of the UN Security Council’s remit, reversing what he called “illegal resolutions” passed by the world body.
The long-sought accord came after 18 days of talks in Vienna, the culmination of 22 months of diplomacy between Iran and the P5+1 group — Britain, China, France, Russia and the United States plus Germany.
In a message posted on his Twitter account before the deal was formally unveiled in Vienna, Rouhani said “new horizons” could open now that “this unnecessary crisis” has been resolved.
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.
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 the economy.
The deal puts strict limits on Iran’s nuclear activities for at least a decade and calls for stringent UN oversight, with world powers hoping this will make any dash to an atomic bomb virtually impossible.
Iran has always denied Western suspicions that it has been trying to acquire the know-how to make nuclear weapons and Rouhani reiterated that stance Tuesday.
“Iran will never seek a nuclear weapon, with or without the implementation” of the Vienna deal, he said, adding that to do so was against the Islamic republic’s religion and such a course would contradict a fatwa from supreme leader Ayatollah Ali Khamenei.