Last Updated Jan 16, 2016 8:45 PM EST
The head of the U.N. nuclear agency has confirmed that Iran has met its obligations under a landmark nuclear deal reached with six world powers.
Certification by the International Atomic Energy Agency will allow Iran to immediately recoup some $100 billion in assets frozen overseas. Iran will also see huge benefits from new oil, trade and financial opportunities after Western sanctions against it are lifted.
Saturday afternoon, President Obama signed executive orders lifting economic sanctions on Iran and Federica Mogherini, the European Union's foreign policy chief, said the EU had lifted its nuclear-related sanctions as well.
"Today marks the first day of a safer world," Secretary of State John Kerry said. He said the nuclear agreement was a reminder "once again of diplomacy's power to tackle significant challenges."
IAEA director general Yukiya Amano says Saturday this means "relations between Iran and the IAEA now enter a new phase. It is an important day for the international community. I congratulate all those who helped make it a reality."
The spokesman for U.N. Secretary General Ban Ki-moon called it "a significant milestone that reflects the good faith effort by all parties to fulfill their agreed commitments."
"This achievement demonstrates that international proliferation concerns are best addressed through dialogue and patient diplomacy," the U.N. said in a statement. "The Secretary-General hopes the success of this agreement contributes to greater regional and international cooperation for peace, security and stability in the region and beyond."
"With the green light to begin the lifting of U.S. and European Union sanctions and verification under the U.N. nuclear agreement, verification will now rest squarely with the International Atomic Energy Agency," CBS News' Pamela Falk reports. "The submission of the report on compliance triggered the start of the Iran nuclear agreement without further action by the U.N. Security Council, which approved the plan in July as Resolution 2231."
"The U.N. deal will now begin, with years of verification required by the U.N.'s nuclear watchdog agency, at the same time that the U.S. and Europe will give Iran access to $100 billion, by allowing it access to its assets frozen overseas and lifting of sanctions on Iranian products," Falk said.
Iranian President Hassan Rouhani congratulated the Iranian nation.
"Thank God for this blessing and bow to the greatness of the patient nation of Iran. Congrats on this glorious victory," Rouhani tweeted.
The landmark Iran nuclear agreement, struck after decades of hostility, defused the likelihood of U.S. or Israeli military action against Iran, something Iranian Foreign Minister Mohammad Jawad Zarif alluded to.
"Our region has been freed from shadow of an unnecessary conflict that could have caused concerns for the region," he said. "Today is also a good day for the world. Today will prove that we can solve important problems through diplomacy."
Iran insists all of its nuclear activities are peaceful. But under the July 14 deal, it agreed to crimp programs which could be used to make nuclear weapons in return for an end to sanctions. The agreement puts Iran's various nuclear activities under IAEA watch for up to 15 years, with an option to re-impose sanctions should Tehran break its commitments.
Earlier, as diplomatic maneuvering on the nuclear issue dragged on into the evening, progress came on another area of Iran-U.S. tensions: U.S. and Iranian officials announced that Iran was releasing four detained Iranian-Americans in exchange for seven Iranians held or charged in the United States.
U.S. officials said the four Americans, including Washington Post reporter Jason Rezaian, former Marine Amir Hekmati, pastor Saeed Abidini and Nosratollah Khosravi-Roodsari, whose name had not been previously made public, were to be flown from Iran to Switzerland on a Swiss plane and then brought to a U.S. military hospital in Landstuhl, Germany, for medical treatment.
In return, the U.S. will either pardon or drop charges against seven Iranians - six of whom are dual citizens - accused or convicted of violating U.S. sanctions. The U.S. will also drop Interpol "red notices" - essentially arrest warrants - on 14 Iranian fugitives it has sought.
Rezaian is a dual Iran-U.S. citizen convicted of espionage by Iran in a closed-door trial in 2015. The Post and the U.S. government have denied the accusations, as has Rezaian.
Iran also committed to cooperate with the U.S. to determine the whereabouts of Robert Levinson, who disappeared in Iran in 2007, the officials said.