Negotiators from Iran and major world powers reached agreement on a framework for a final agreement to curb Tehran's nuclear program in exchange for relief from international sanctions, participants in the talks said. (Yahoo News)

At last, it's happened in Lausanne. Iranian diplomats and their counterparts from six world powers, including the United States, have emerged with a "Joint Comprehensive Plan of Action" regarding Iran's nuclear program. This framework of an agreement -- the final deal is supposed to be reached by June 30 -- has been the product of days of intense, closed-door negotiations.

WorldViews explained earlier this week the main sticking points to a deal, which needs to satisfy Western fears over Iran's ability to build a nuclear weapon, while providing Iran sanctions relief and allowing it to maintain a peaceable nuclear program. There's still plenty of work to be done, but the diplomatic efforts of the United States and its interlocutors could now lead to a historic opening with the Islamic Republic, whose leadership -- at least some figures within it -- are desperate for closer ties with the West.

Analysts appear surprised by the thoroughness of this framework agreement, which gives proponents of a deal hope that a real pact may be sealed this summer. Here's what you need to know about what this current round of talks has set in place.

[The key moments in the long history of U.S.-Iran tensions.]

1. The main metric bandied about when calculating how to prevent an Iranian atomic bomb is "breakout time" -- that is, the time it would take for Iran to produce enough fissile material (highly enriched uranium) that could make one nuclear weapon. The importance of breakout time as the main criterion to understanding Iran's nuclear ambitions is a matter of debate, and some experts say it's a bit pointless to obsess over it.

But one of the chief goals of any U.S.-backed agreement has been to extend Iran's supposed breakout time from an estimated two to three months right now to at least a year. A larger window gives the international community more time to respond and take tougher action on Iran. And the assumption is that the harder it is for Iran to produce a weapon, the less likely the chance that it will.

2. As far as the United States and its partners are concerned, the measures announced  Thursday are centered on making it difficult for Iran to both produce and maintain stocks of highly enriched uranium. Iran has already diluted its stockpile of uranium enriched at 20 percent and agreed to dramatically reduce other stockpiles of low-enriched uranium. But stricter measures are necessary to prevent any move toward a weapon. (You can see a diagram that shows how uranium gets enriched here.)

3. One way of controlling this is capping Iran's number of centrifuges -- the whirling devices that enrich uranium gas. Under terms outlined  Thursday, Iran will reduce its centrifuges from some 19,000 to 6,104. According to a memorandum circulated by American officials, Iran has agreed that, for the next 10 years, it will enrich uranium at only one facility, in Natanz, which has 5,000 first-generation centrifuges. It will not enrich uranium at levels beyond 3.67 percent -- insufficient for a bomb, but useful for nuclear energy purposes -- for 15 years.

4. Iran appears willing also to suspend enrichment activity at the controversial Fordow nuclear facility for 15  years, and will apparently convert the site into a nuclear physics research center. Fordow, situated inside a mountain outside the holy city of Qom, has particularly worried American and Israeli officials. Iranian authorities will guarantee that the heavy-water reactor in Arak, a site where it's feared Iran intends to produce weapons-grade plutonium, will not do so.

5. A very tight regime of international inspections will be imposed. Inspectors from the IAEA, the U.N. nuclear watchdog, will continuously monitor Iran's centrifuges and nuclear storage facilities for two decades, will have regular access to uranium mines and mills for the next 25 years, and will be able to conduct regular checks on Iran's nuclear sites. "If Iran cheats, the world will know it," said President Obama on Thursday.

6. In return, Iran wins sanctions relief, depending on its ability to follow through with the commitments agreed upon in a final deal. This will likely not happen as swiftly as the Iranians would like, and there seems to be a mechanism by which the sanctions would automatically "snap back" in place should Iran violate the terms of an agreement.

But the promise of the United States and European Union eventually lifting oil and banking sanctions on Iran led to celebrations in Tehran and a dip in the global price of oil on Thursday.

Iranians celebrated on the streets of Tehran following the announcement that a framework agreement has been reached on Iran's nuclear program between the country and the major world powers. (The Washington Post)

7. Other issues -- including to what extent Iran can use and upgrade more advanced centrifuges, as well as what happens to other military dimensions of its nuclear program -- still need ironing out in the months ahead.

8. The optimism generated by this framework agreement will not be shared by hawks in the United States and Israel, as well as in the Arab states, who still consider Iran a dangerous regional threat. Opponents of a deal in the United States may step up efforts to derail the talks in the coming weeks in Congress.

But the Obama administration can point to a pretty solid agreement that keeps Iran's nuclear ambition "in an iron box," and establishes the means by which the international community may be able to ensure it stays there.

In an agreement that he called "a long time coming," President Obama announced that the U.S., Iran and other countries have reached a historic framework to curb Iran's nuclear program. (AP)

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