World powers and Iran have formally announced a comprehensive nuclear accord.
Federica Mogherini, the European Union's foreign policy chief, said: "Today is an historic day."
She added that it was a great honour "for us to announce that we have reached an agreement on the Iranian nuclear issue".
Today's nuclear deal with Iran will be "centre stage" in Barack Obama's legacy as President, ITV News International Affairs Editor Rageh Omaar says.
In his video blog, Omaar says the agreement is the first international deal of its kind to have been "personally driven" by a US President since Jimmy Carter helped broker the Camp David Accords between Egypt and Israel in the 1970s.
Despite likely opposition from the Republican-led Congress, Omaar says the President will use his veto to pass the deal into law.
He adds, however: "The question is, will it out-survive whoever becomes the next President of the United States in November 2016?"
Prime minister Netanyahu has likened the nuclear deal with Iran to the unsuccessful 1994 deal on North Korea's nuclear programme.
An end to Iranian nuclear question could soon be a reality after years of hard and often tense negotiations.