The agreement limits Iranian nuclear activity in exchange for billions of dollars in sanctions relief.

Iranians are declaring online that the deal is a victory, posting ‎#IranWinsPeace in thousands of tweets and Instagram posts since Monday. "I hope that good days are waiting for us," someone tweeted from Tehran, using the hashtag. "The Iranians showed that they are civilized and rational people."

Final talks in Vienna involved nearly three weeks of intense round-the-clock talks. The deal is a major policy victory for both U.S. President Barack Obama and Iranian President Hassan Rouhani, a pragmatist who has vowed to reduce Iran's diplomatic isolation.

EU foreign policy chief Federica Mogherini declared the deal "a sign of hope for the entire world." Iranian Foreign Minister Mohammad Javad Zarif called it a "win-win solution" that builds a "new chapter of hope," the Associated Press reported.