LAUSANNE, Switzerland (AP) — Sticking points in the negotiations between world powers and Iran over scaling back Tehran's nuclear program in exchange for removing economic penalties.
Diplomats have extended the talks beyond a March 31 deadline for the outline of a deal.
U.S. Secretary of State John Kerry extended his stay at the talks until at least Thursday.
The United States and others in the negotiations have cited enough progress to keep at it.
The United States says any deal will stretch the time Iran would require to make a nuclear weapon, to at least year from two months to three months now.
Critics are skeptical and say such an agreement would keep intact Tehran's nuclear technology.
The sides have made progress on cuts and limits to Iran's enrichment program. Over the past weeks, Iran has moved from demanding that it be allowed to keep nearly 10,000 centrifuges enriching uranium to agreeing to 6,000.
Tehran may be ready to accept even fewer but is said to be pushing back on how long it must limit the technology it could use to make atomic arms.
WHERE ELSE IS THERE PROGRESS?
Iran and the six powers at the table have edged closer about what to do with a nearly built Iranian reactor. It was a proliferation concern because it would have produced enough plutonium for several nuclear bombs a year.
The facility would be re-engineered to generate only a fraction of the material.
Officials say the sides also are discussing turning a formerly secret underground uranium enrichment plant into a facility that would make isotopes for medical, industrial and scientific uses.
If used for uranium enrichment, the bunker would be a concern because it is thought impervious to air attack.
Although it would not be enriching uranium, the facility would use the same technology as for uranium enrichment. Critics say that leaves potential bomb-making infrastructure intact.
WHERE ARE THE GREATEST PROBLEMS?
The sides differ sharply on how and when to lift the sanctions after nearly a decade.
Iran long has pushed to have for that to happen as soon as a deal reached. But Deputy Foreign Minister Abbas Araghchi on Wednesday suggested Tehran may be content with an immediate end to economic penalties and a separate arrangement for U.N. sanctions.
The U.S. and its allies want it done gradually over much of the length of any agreement, if not all of it. That way, they can use sanctions as a lever in case Tehran reneges on any commitments.
Iran's research and development of centrifuges and related technology also is in dispute.
Iran wants few, if any limits. The other side sees potentially major advances as a problem that would counter the idea of freezing activities that could be applied to nuclear weapons manufacture.
On the length of a deal, Iran insists on 10 years. It is resisting a push to extend that time by at least five more years of slowly easing restrictions on its program.
WHAT'S OFF THE TABLE?
The six powers originally insisted that any final deal include a ruling by the U.N.'s International Atomic Energy Agency on allegations that Tehran has worked secretly in the past on nuclear arms. Iran denies it, saying the allegation is based on intelligence doctored by its foes.
The IAEA investigation is deadlocked and Iran is offering no indications it will cooperate. Any agency findings probably will be delayed for months, if not years, much too late for the June deadline.
Washington and its allies initially said Iran must agree to restrictions on its missile technology, which they say could be used to deliver a nuclear warhead. Tehran has resisted including this matter in the talks; diplomats say the topic has not been part of formal discussions for weeks.