The U.S. is sending another 1,000 troops to the Mideast as Iran plans to break an accord limiting nuclear development. Here's how we got here.
The latest from today's developments
U.S. officials say the Pentagon is sending about 1,000 additional American troops to the Middle East, as commanders try to bolster security for forces and allies in the region from what authorities say is a growing threat from Iran.
Meanwhile, Iran announced it will exceed the uranium stockpile limit set by Tehran's nuclear deal with world powers in the next 10 days, further escalating the tensions in the Mideast.
Officials say the deployment includes security forces and troops for additional surveillance and intelligence gathering in the region.
The troops are part of a broader military package of options that were initially laid out to U.S. leaders late last month, totaling as much as 10,000 forces, Patriot missile batteries, aircraft and ships.
The latest decision comes as Secretary of State Mike Pompeo and other top officials reach out to leaders in Asia and Europe to convince them that Iran was behind alleged attacks on shipping along a Middle East oil route.
Meanwhile, Iran announced it will exceed the uranium stockpile limit set by Tehran's nuclear deal with world powers in the next 10 days, further escalating tensions in the Mideast.
Iran's June 27 deadline comes ahead of another, July 7 deadline for Europe to come up with better terms for Iran to stay in the accord. If that second deadline passes without any action, Iranian President Hassan Rouhani says the Islamic Republic likely will resume higher uranium enrichment.
Here's where Iran's unravelling nuclear program now stands.
The nuclear deal that is now unraveling
Iran struck the nuclear deal in 2015 with the United States, France, Germany, the United Kingdom, Russia and China. The deal, formally known as the Joint Comprehensive Plan of Action, grew out of secret talks President Barack Obama's administration held with Iran after Rouhani, a relative moderate, took office.
Iran agreed to limit its enrichment of uranium under the watch of U.N. inspectors in exchange for the lifting of economic sanctions. International businesses rushed to do deals with Iran, most notably the billion-dollar sales by Airbus and Boeing Co.
President Donald Trump, who campaigned on a promise of tearing up the deal because it didn't address Iran's ballistic missile program or its involvement in regional conflicts, withdrew America from the accord in May 2018. That halted promised international business deals and dealt a heavy blow to Iran's already anemic economy. In the time since, the Trump administration has said any country that imports Iranian crude will face U.S. sanctions.
Where are the nuclear stashes?
Natanz, in Iran's central Isfahan province, hosts the country's main uranium enrichment facility, located underground. Iran has one operating nuclear power plant in Bushehr, which it opened with Russia's help in 2011. Under the accord, Iran reconfigured a heavy-water reactor so it couldn't produce plutonium and agreed to convert its Fordo enrichment site — dug deep into a mountainside — into a research center. Iran said on Monday it may stop the heavy-water reactor reconfiguration. Tehran also operates an over 50-year-old research reactor in Tehran.
Under terms of the nuclear deal, Iran can keep a stockpile of no more than 300 kilograms (660 pounds) of low-enriched uranium. That's compared to the 10,000 kilograms (22,046 pounds) of higher-enriched uranium it once had. Currently, the accord limits Iran to enriching uranium to 3.67%, which can fuel a commercial nuclear power plant. Weapons-grade uranium needs to be enriched to around 90%. However, once a country enriches uranium to around 20%, scientists say the time needed to reach 90% is halved. Iran previously has enriched to 20%. Iranian officials say they've quadrupled their production of low-enriched uranium and will break the 300-kilogram limit by June 27.
What are Iran's capabilities?
A centrifuge is a device that enriches uranium by rapidly spinning uranium hexafluoride gas. Under the atomic accord, Iran has been limited to operating 5,060 older-model IR-1 centrifuges. The IR-1 is based on a 1970s Dutch design that Pakistani scientist A.Q. Khan used to build Islamabad's nuclear weapons program and later sold to Iran, Libya and North Korea.
Iran has the technical ability to build and operate advanced versions called the IR-2M, IR-4 and IR-6 at Natanz, but is barred from doing so under the nuclear deal. Ali Akbar Salehi, the head of Iran's nuclear program, told The Associated Press in September that the IR-2M and the IR-4 can enrich uranium five times faster than an IR-1, while the IR-6 can do it 10 times faster. Western experts have suggested these centrifuges produce three to five times more enriched uranium in a year than the IR-1s.
Iran also mothballed many already-built centrifuges as part of the deal.
Rising tensions, from 'atoms for peace' to Stuxnet
Iran's nuclear program actually began with the help of the United States. Under its "Atoms for Peace" program, America supplied a test reactor that came online in Tehran in 1967 under the rule of Shah Mohammad Reza Pahlavi. That help ended once Iran's 1979 Islamic Revolution overthrew the shah.
In the 1990s, Iran expanded its program, including buying equipment from A.Q. Khan. Among its activities, Iran "may have received design information" for a bomb and researched explosive detonators, according to the International Atomic Energy Agency.
By August 2002, Western intelligence services and an Iranian opposition group revealed a covert nuclear site at Natanz. Iran to this day denies its nuclear program had a military dimension. Iran suspended enrichment in 2003 but resumed it three years later under hard-line President Mahmoud Ahmadinejad. World powers imposed crippling U.N. sanctions in response. The Stuxnet computer virus, widely believed to be a joint U.S.-Israeli creation, soon disrupted thousands of Iranian centrifuges.
A string of bombings, blamed on Israel, targeted a number of scientists beginning in 2010 at the height of Western concerns over Iran's program. Israel never claimed responsibility for the attacks, though Israeli officials have boasted in the past about the reach of the country's intelligence services. Israel last year said it seized records from a "secret atomic archive" in Iran.
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Timeline: Key events raising tensions in the Persian Gulf
Tensions between the United States and Iran have soared in recent weeks, with Washington dispatching warships and bombers around the Persian Gulf, and Tehran threatening to resume higher uranium enrichment. The tensions come a year after President Donald Trump withdrew from Iran's 2015 nuclear accord with world powers and restored crippling sanctions.
A timeline of recent events:
May 5: John Bolton, the White House national security adviser and a longtime Iran hawk, announces the deployment of the USS Abraham Lincoln carrier strike group and a bomber task force in response to "a number of troubling and escalatory indications and warnings," without providing details. He threatens "unrelenting force" in response to any attack.
May 8: Iran vows to enrich its uranium stockpile closer to weapons-grade levels, starting July 7, if world powers fail to negotiate new terms for its nuclear deal. The U.S. responds by imposing sanctions on Iran's metal industry.
May 9: The European Union urges Iran to respect the nuclear deal and says it plans to continue trading with the country despite U.S. sanctions. Trump says he would like Iran's leaders to "call me."
May 10: The U.S. says it will move a Patriot missile battery into the Middle East to counter threats from Iran.
May 12: The United Arab Emirates says four commercial ships off its eastern coast "were subjected to sabotage operations," just hours after Iranian and Lebanese media outlets air false reports of explosions at a nearby Emirati port.
May 13: European foreign ministers urge the United States and Iran to show restraint, while U.S. Secretary of State Mike Pompeo briefs his counterparts on the alleged threats from Iran. Trump warns that if Tehran does "anything" in the form of an attack, "they will suffer greatly."
May 14: Yemen's Iran-aligned Houthi rebels launch a drone attack on Saudi Arabia, striking a major oil pipeline and taking it out of service.
— The New York Times reports the White House is reviewing military plans that could result in sending 120,000 U.S. troops to the Middle East if Iran attacks American forces or steps up work on nuclear weapons. Trump says it's "fake news," but that he would "absolutely" be willing to send troops if necessary.
— Iran's Supreme Leader Ayatollah Ali Khamenei says "no one is seeking war," but that it wouldn't be difficult for Iran to enrich uranium to weapons-grade levels.
— A senior military officer in the U.S.-backed coalition fighting the Islamic State group says "there's been no increased threat from Iranian-backed forces in Iraq and Syria." In a rare public rebuttal, U.S. Central Command says his remarks "run counter to the identified credible threats."
May 15: The U.S. Embassy in Baghdad orders all nonessential government staff to leave Iraq immediately. The Netherlands and Germany say they are suspending their training of Iraqi forces.
May 16: Saudi Arabia blames Iran for the drone attack on its pipeline and an English-language newspaper close to the palace calls for the U.S. to launch "surgical" strikes in retaliation.
—Trump says he hopes the U.S. is not on a path to war with Iran amid fears that his two most hawkish advisers could be angling for a conflict with the Islamic Republic. Asked if the U.S. was going to war with Iran, the president replied, "I hope not" — a day after he repeated a desire for dialogue, tweeting, "I'm sure that Iran will want to talk soon."
May 19: A rocket lands near the U.S. Embassy in Baghdad, without harming anyone. It's not clear who is behind the attack, but after the initial reports, Trump tweets: "If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!" Iran's foreign minister responded by tweeting that Trump had been "goaded" into "genocidal taunts."
May 20: Semi-official media in Iran report that it has quadrupled its production of low-enriched uranium, which is used for civilian applications but not nuclear weapons. Iran is allowed to enrich uranium to the low level of 3.67%, but increased production could lead it to exceed the stockpile limits in the nuclear deal.
May 24: Trump says the U.S. will bolster its military presence in the Middle East with an additional 1,500 troops. He says the troops will have a "mostly protective" role.
— Senior Pentagon officer Vice Admiral Michael Gilday says the U.S. has a high degree of confidence that Iran's Revolutionary Guard was responsible for the explosions of the four tankers in the Gulf of Oman, and that Iranian proxies in Iraq fired rockets into Baghdad.
May 31 and June 1: Saudi Arabia's King Salman hosts three high-level summits in Mecca, drawing heads of state from across the Middle East and Muslim countries to present a unified Muslim and Arab position on Iran. The monarch calls on the international community to use all means to confront Iran and accuses the Shiite power of being behind "terrorist operations" that targeted Saudi oil interests.
June 12: Saudi Arabia says 26 people were wounded in an attack by Yemen's Houthi rebels targeting an airport in kingdom's southwestern town of Abha. The Houthis claim they'd launched a cruise missile at the airport.
June 13: Two oil tankers near the strategic Strait of Hormuz are hit in an alleged assault that leaves one ablaze and adrift as 44 sailors are evacuated from both vessels and the U.S. Navy rushes to assist. America later blames Iran for the attack, something Tehran denies.
June 17: Iran says it will break the uranium stockpile limit set by Tehran's nuclear deal with world powers in the next 10 days.