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Iran and six world powers have already agreed on how Tehran should limit its nuclear activities, and they're working out the details. But differences remain over what Iran will get in return.

After a whirlwind few days in Geneva, Iran and six world powers — the United States, Russia, China, Britain, France and Germany — have walked away from talks on Iran's nuclear program with only a vow to return in 10 days.

But behind the scenes a lot was accomplished, according to diplomats in Geneva for the talks, who spoke only on condition of anonymity because they weren't authorized to discuss diplomatic maneuvering.

WHAT IS THE DISPUTE?

Iran has produced tons of low-enriched uranium and nearly 200 kilograms (450 pounds) of uranium enriched to 20 percent; the latter could be turned into weapons-grade uranium to arm nuclear warheads much more quickly. Iran has also started to build a plutonium-producing reactor. The six nations originally wanted Iran to suspend all enrichment, but are now trying only to contain its work. They have imposed crippling sanctions on Iran to press their case.

WHAT DOES THE OFFER ON THE TABLE LOOK LIKE?

Iran would downgrade all of its 20-percent enriched uranium to 5 percent — the grade needed for reactor fuel — and limit all future production to the same level. It would also delay work on the plutonium reactor for six months.

The six nations, in turn, would unfreeze some of the tens of billions of dollars Iran holds in overseas bank accounts. They also would lift some of the sanctions — specifically those limiting trade in precious metals and petrochemicals.

WHAT MORE DOES IRAN WANT?

Tehran wants more of the sanctions lifted — the "core" oil sanctions that cripple its ability to sell its main export. It also wants the six world powers to let it resume international financial transactions immediately.

WHAT ARE THE OTHER STICKING POINTS?

The six world powers don't always agree. Over the weekend, France suddenly voiced opposition to the demand that work stop for six months on Iran's plutonium reactor, saying that isn't enough. The differences were resolved after pressure from France's negotiating partners.

The other main issue is Iran's claim that it has a right to a peaceful enrichment program. The United States and Britain oppose this, while Russia, China — and now even France — feel the world powers should concede the point to Tehran.

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Associated Press writer Greg Keller contributed from Paris.