World powers signed off Saturday on a historic deal that curbs Iran's nuclear weapons-building, eases economic sanctions that have long crippled the Islamic Republic and rewrites diplomatic dynamics throughout the Middle East.
Tens of billions of dollars will soon be available to Iran, as well as access to the international banking system and global markets for the sale of oil and gas for the first time in years, greatly bolstering its ability to rejoin the world economy.
President Obama immediately issued an executive order canceling numerous sanctions levied by the U.S.
The deal, coupled with a secretly negotiated swap that freed prisoners including Washington Post reporter Jason Rezaian, signals a new, if still tentative, era of cooperation between Washington and Tehran after decades of sharp-edged acrimony.
"Today marks the first day of a safer world," Secretary of State John F. Kerry said in Vienna after the United Nations' nuclear watchdog, headquartered there, certified that Iran had complied with significant steps aimed at dismantling its nuclear production capabilities and had agreed to the most rigorous inspections on Iranian soil to date.
"Today marks the moment that the Iran nuclear agreement transitions from an ambitious set of promises on paper to measurable action in progress," Kerry added.
Word of the U.N. certification rang out from Vienna to the capitals of the negotiating countries; on the campaign trail, where Republicans were quick both to praise the Americans' release and to decry the administration's negotiating techniques; and in Los Angeles, home to the world's largest Iranian expat community.
The two countries have been bitter enemies since Iranian Islamic revolutionaries seized the U.S. Embassy in Tehran in 1979 and took hostages. No one is expecting the renewal of diplomatic ties any time soon — indeed, sanctions remain in place tied to Iran's human-rights record and funding of groups the U.S. views as terrorists — but the Obama administration credited a newfound rapprochement with seeing the nuclear deal to fruition as well as securing the freedom of the American prisoners.
That same spirit, which experts agree has to have been approved by Iranian Supreme Leader Ali Khamenei, also led to the quick release last week of 10 U.S. sailors detained in Iranian waters. What might have become a major international incident a few years ago was resolved within hours.
Even as Washington's relationship with Tehran seems on a smoother course — Kerry and his Iranian counterpart, Mohammad Javad Zarif, are on the phone just about daily — the United States' longest-standing allies in the region, Saudi Arabia and Israel, have appeared increasingly on the outs.
Both Saudi Arabia and Israel opposed the nuclear deal, saying Iran could not be trusted and fearing a less-isolated Iran able finally to join the world economic and political stage. The governments of both are notoriously distrustful of and unfriendly with the Obama administration. U.S. officials can point to more fruitful talks with Iran while relations with Israel and the Saudis have turned increasingly frigid.
That Iran has been cooperative also reflects its desire to emerge from its long status as pariah state, as well as an apparent ascendancy, for now, of Iranian moderates, including Zarif and President Hassan Rouhani. They hoped to show gains to their public before elections next month.
The biggest carrot, of course, was the release of billions of dollars — $50 billion immediately that has been held in Asian banks, and then other income from finally being allowed to sell its oil and gas on the open market.
The major test now will be whether relations between Iran and the U.S. evolve to encompass broader issues. Iran could cooperate on untangling the complex conflicts in the region, such as the civil war in Syria, where Tehran backs President Bashar Assad.
"There is momentum; how do you translate that into a new turning point?" Fawaz Gerges, author of "The New Middle East: Protest and Revolution in the Arab World," said on CNN.
The Obama administration argued that the deal will impede Iran's ability to build a nuclear bomb for years. It has hailed the deal as the epitome of successful foreign diplomacy.
Republican presidential candidates and other opponents attacked the deal and, while welcoming the return of the prisoners, said the U.S. should not engage in such swaps and the freed men should never have been allowed to languish in jail as long as they did.
"It tells us all we need to know about the Iranian regime," Sen. Marco Rubio told reporters in Johnston, Iowa, after a campaign event. "They take people hostage to gain concessions. And the fact they can get away with it with this administration has created an incentive for more governments to do this."
House Speaker Paul D. Ryan attacked the deal, saying the release of the money will allow Iran to "fund terrorism."
Even Hillary Clinton, Obama's former secretary of State under whose tenure the Iran talks started, was less than enthusiastic.
While she welcomed the "safe return" of the prisoners and praised the implementation of the nuclear agreement as "an important achievement of democracy backed by pressure," she added: "We shouldn't thank Iran for the prisoners or for following through on its obligations."
She noted that Iran has violated other U.N. resolutions with its ballistic missile program, including several recent launches. The Obama administration contemplated new sanctions then but backed down, possibly to avoid derailing the nuclear deal.
"So we can't take our eye off the ball," Clinton said.
Administration officials took pains to say the negotiations for the release of the prisoners were conducted on a separate track from the nuclear deal. However, they said the nuclear talks fostered relationships and increased access to Iranian intelligence and other officials that made the prisoner release possible.
To meet its obligations, Iran had to remove the core of its plutonium-producing heavy water reactor at Arak, then fill the reactor with cement and destroy it; dismantle or mothball thousands of centrifuges, which are used to enrich uranium; and ship nearly its entire stockpile of enriched uranium to Russia for reprocessing.
Iranian and U.S. officials have said all these steps have been taken, more than tripling the time Iran would need to produce a single nuclear weapon.
The government in Tehran will quickly gain access to more than $50 billion in frozen assets and oil revenue. The U.S. embargo on trade with Iran will continue, but several exceptions will be allowed, including the import and export of food and carpets.
Four hundred Iranian individuals will be removed from U.S. government blacklists, while Europe will allow trade in software, gold and metals, and transportation equipment.
In recent months, business delegations from Europe, Asia and elsewhere have been making the rounds in Tehran with an eye toward new business opportunities in the nation of 80 million, which has long been economically isolated because of sanctions.