The United States and five other world powers have reached a deal with Iran that would place strict limits on Tehran’s nuclear program in return for ending sanctions on its economy, the culmination of years of delicate diplomacy pursued by President Barack Obama despite warnings the agreement could strengthen Iran’s Islamist regime and leave it dangerously close to a nuclear bomb.

The historic accord, reached by Secretary of State John Kerry and his international counterparts in Vienna on Tuesday after 18 days of intense negotiations, now faces review from a hostile Republican-led Congress, opposition from every GOP presidential candidate, from Israel’s government and from Sunni Arab monarchs. The deal’s long and complex implementation process also leaves it vulnerable to unraveling.


Speaking from the White House Tuesday morning, Obama called the deal a victory for diplomacy that would prevent a nuclear arms race in the Middle East and avert a possible conflict with Iran.

“No deal means a greater chance of more war in the Middle East,” Obama said. He reaffirmed America’s commitment to Israel’s security and Gulf Arab states like Saudi Arabia, while adding that the U.S. is “open to engagement on the basis of mutual interests and mutual respect.”

Obama also hinted at the possibility of a larger thaw in U.S.-Iranian relations. ”It is possible to change,” Obama told Iranians, urging them to take a “different path, one of tolerance, of peaceful resolution to conflict… This deal opens an opportunity to move in a new direction. We should seize it.”

“This is the good deal that we have sought,” Kerry said in a statement from Vienna.

If it succeeds, the agreement could upgrade Obama’s checkered foreign policy legacy, as well provide a crowning achievement for Kerry’s 30-year political career. Analysts call it one of the modern era’s most important arms control agreements, in a league with the 1970 international Nuclear Non-Proliferation Treaty and the 1994 START nuclear missile treaty between the U.S. and the Soviet Union.

Some believe it could begin to normalize relations between Iran and the West after three decades of cold war, although Obama and Kerry have denied that is their goal, while others predict that an emboldened Iran will seek greater dominance across the Middle East. But on Tuesday the European Union’s top foreign policy official, Frederica Mogherini, called the pact “much more than a nuclear deal,” adding: “It can open a new chapter.”

On Twitter, Iran’s president, Hassan Rouhani said that with the “unnecessary crisis resolved, new horizons emerge with a focus on shared challenges.”

That will hardly please Israeli Prime Minister Benjamin Netanyahu, who tweeted: “From the initial reports we can already conclude that this agreement is a historic mistake.”

According to a 159-page document posted online by Russia’s foreign ministry, which it called the final text of the deal, a U.N. resolution lifting sanctions will also express the Security Council’s “desire to build a new relationship with Iran.”

The text says also that Iran has vowed that “under no circumstances” will it ever “seek, develop or acquire any nuclear weapons.” And it describes a joint commission composed of its seven parties to monitor the deal’s implementation.

One issue that will draw close scrutiny from nuclear experts is Iran’s ability to research advanced nuclear technologies while its program is constrained by a deal. Iran now relies on 1970s-era centrifuges to enrich uranium, which are highly inefficient. The document posted by Russian foreign ministry says that after 8½ years Iran can begin testing up to 30 modern IR-6 and IR-8 centrifuges. Analysts fear that, if Iran masters top-quality centrifuges, it might be capable of producing a bomb in a matter of months or weeks soon after the deal’s main restrictions lift in a decade.

On an issue that snagged the talks in their final days, the deal will free Iran from an arms embargo after five years, Obama said Tuesday.

Obama has made the deal a central plank of his foreign policy. Dating from early in the 2008 presidential campaign, he called for fresh thinking toward American adversaries like Iran. As president, he has argued that it is wiser to negotiate with a nemesis of more than three decades than risk a military confrontation over Iran’s nuclear ambitions.



But he has also insisted, in response to the many critics who called him desperate for a deal, that signing off on a weak agreement is not in his interest. “If Iran has a nuclear weapon, it’s my name on this,” the president said in May — a measure of just how keenly aware he is of the deal’s implications for his legacy.

The deal came 18 days after Kerry arrived in Vienna for a round of talks whose initial deadline was June 30. As early July came and went, the talks bogged down in a handful of issues, including whether and how to lift a U.N. embargo on Iran’s import and export of conventional arms.

Kerry, too, was accused of wanting a deal too badly, a charge his marathon session in Vienna — all of it on crutches, as he recovers from a broken leg — may have defused.

The comprehensive deal fills in the details of a preliminary framework deal reached in April by the U.S. and its negotiating partners — France, Germany, Britain, China and Russia. A document said to be about 100 pages will be transmitted to Congress and made public, although some portions are expected to remain classified.

Obama’s main goal has been to impose limits on Iran’s fast-advancing nuclear program to ensure that Tehran can’t acquire a nuclear bomb faster than the U.S. and its allies can act to stop it. The deal seeks to do that by reducing Iran’s capacity to produce highly enriched uranium and plutonium, slowing its research and development into nuclear technology, and imposing inspections and monitoring of Iran’s nuclear activities to prevent cheating.

The goal is to achieve a “breakout time” — or the time it would take Iran to produce the nuclear material required for one bomb — of at least one year. That is long enough, U.S. officials believe, for the world community to take punitive action that could include airstrikes against Iranian facilities.

Some elements of the deal were locked in by an April 2 political framework agreement reached in Lausanne, Switzerland. They include a commitment by Iran to reduce its number of installed centrifuges from 19,000 to 6,104, with only 5,060 of those enriching uranium for 10 years. Centrifuges spin gaseous uranium at supersonic speeds to increase its purity to levels suitable for a nuclear weapon.

Iran has also agreed to modify a plutonium-fueled nuclear reactor so that its fuel cannot be reprocessed for use in a weapon. And it will allow inspectors from the International Atomic Energy Agency broad access to suspected nuclear sites, as well as cooperate with an IAEA investigation into its past activities, although many crucial details have yet to be released.

The comprehensive agreement will leave many powerful critics deeply dissatisfied. Netanyahu, who sees Iran as an existential threat to his country, has said repeatedly that the deal will “pave Iran’s path to the bomb”; several Sunni Arab states, especially Saudi Arabia, worry that the end of sanctions will free up tens of billions of dollars that Iran can direct to militant allies like Hezbollah and sectarian battles from Iraq to Syria to Yemen.

The emerging outlines of the deal have also drawn withering fire for months from Capitol Hill, fueled by Republicans — and many Democrats — who agree with Netanyahu that it jeopardizes Israel’s security. A vote of disapproval by Congress would prevent Obama from lifting sanctions on Tehran, although administration officials believe they can maintain enough Democratic backing to sustain a presidential veto.

The nuclear talks began after years of Western worry over Iran’s nuclear aims, despite Tehran’s insistence that its program was only for scientific and energy purposes.

The 2002 revelation of Iran’s uranium enrichment plant at Natanz and a plutonium reactor at Arak — sites previously undeclared to the U.N. in violation of Iran’s international commitments — badly undercut Tehran’s claims. So did the 2009 discovery of a secret, underground enrichment facility buried in a mountain at Fordow, near the holy city of Qom.

In 2007, an assessment by the U.S. intelligence community found that Iran had pursued a military dimension to its nuclear program — in effect, an Iranian Manhattan Project — but ceased the work in 2003. Iran has failed to comply fully with IAEA inspectors pursuing the question, a major point of contention in the talks.

The United States, which broke off diplomatic relations with Iran after the country’s 1979 Islamic revolution and capture of the U.S. Embassy in Tehran, has long used sanctions and other tools to punish Iran for its behavior. In recent years the sanctions vice tightened considerably as Russia and China backed harsh U.N. measures, the U.S. Congress targeted Iran’s financial sector, and the Obama administration persuaded growing economies like India and South Korea agreed to sharply limit their consumption of Iranian oil.

At the same time, after taking office Obama continued a Bush-era program targeting Iran’s nuclear infrastructure with cyberwar, in the form of the Stuxnet virus, which delayed Iran’s enrichment program.

The U.S., U.N. and EU sanctions badly hurt Iran’s economy; inflation soared above 40 percent in 2013. U.S. sanctions threatening to punish foreign financial institutions for doing business with Iran landed a particularly painful blow.

In mid-2012, after exchanging messages through the Arab state of Oman, Iranian and American officials secretly met to lay the groundwork for potential nuclear talks. This involved diplomats dispatched by then-Secretary of State Hillary Clinton, including her close aide Jake Sullivan, now a top adviser to her presidential campaign.

Talks became possible in June 2013, after Iranians elected as president a relatively moderate Iranian cleric, Hassan Rouhani. He offered the West a more conciliatory face than his hardline predecessor, Mahmoud Ahmadinejad.

With the apparent blessing of Iranian Supreme Leader Ayatollah Ali Khamenei, who has the final word on all state decisions in Iran, Rouhani spoke directly via phone with Obama in September 2013, kicking off the public phase of the nuclear talks.

Despite a willingness to bargain over its nuclear program, Iran has pursued an aggressive foreign policy elsewhere in the Middle East, alarming its neighbors.

For example, Iran is backing Syrian President Bashar Assad against Sunni groups trying to topple him. At the same time, Iranian-trained Shiite militias are indirectly helping U.S.-backed Iraqi troops trying to defeat the Islamic State terrorist group in Iraq. And in Yemen, Iran has backed the Houthi rebels, whose positions are being bombed by Saudi Arabia with U.S. assistance.



Critics of the deal fear that once Iran starts to get relief from sanctions — including access to more than $100 billion in frozen assets — it will use the money to wreak more havoc in the region.

U.S. officials argue that Iran’s regional meddling costs little, and that the country is more likely to direct the influx of funds to repairing its economy and its infrastructure. At the same time, Obama has promised more military aid to Arab countries and repeatedly reaffirmed his commitment to Israel’s security.

In many ways, the hardest part of the nuclear deal begins now, with its implementation.

Congress will review the deal, and is likely to vote to prevent Obama from suspending sanctions on Iran — a measure Obama is sure to veto. In that scenario, the votes of a few dozen Senate Democrats could become decisive in a veto override battle.

The nuclear deal will also drive the 2016 presidential campaign’s foreign policy debate. Several Republican contenders are already vowing to kill the deal if they win the White House.

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