US President Barack Obama said that with the deal, "every pathway to a nuclear weapon is cut off" for Iran.
His Iranian counterpart, Hassan Rouhani, said it opened a "new chapter" in Iran's relations with the world.
Negotiations between Iran and six world powers - the US, UK, France, China, Russia and Germany - began in 2006.
The so-called P5+1 want Iran to scale back its sensitive nuclear activities to ensure that it cannot build a nuclear weapon.
Iran, which wants crippling international sanctions lifted, has always insisted that its nuclear work is peaceful.
There has been stiff resistance to a deal from conservatives both in Iran and the US. The US Congress has 60 days in which to consider the deal, though Mr Obama said he would veto any attempt to block it.
The Republican Speaker of the US House of Representatives, John Boehner, said the deal would only only "embolden" Tehran.
"Instead of stopping the spread of nuclear weapons in the Middle East, this deal is likely to fuel a nuclear arms race around the world," he added.
Israel's government has also warned against an agreement. » | Tuesday, July 14, 2015
