LAUSANNE, Switzerland -- Iran and six world powers say they have reached an agreement on "key parameters" of a comprehensive nuclear agreement that must be finalized by June 30.
EU foreign policy chief Federica Mogherini, reading from a joint statement with Iran at a press conference in Lausanne, Switzerland, said the understanding reached on April 2 is a "decisive step" in the long negotiations to curb Iran's nuclear program in exchange for relief for Tehran from economic sanctions.
She said Iran's uranium-enrichment capacity will be reduced and another facility will be converted into a nuclear physics research center, among other things, in a future agreement.
She said another aspect of the understanding was that a certain amount of enriched uranium already produced would be taken out of Iran.
Mogherini added that the United States and the EU would lift economic sanctions against Iran only after the United Nations, through the International Atomic Energy Agency, verifies that Iran is meeting its obligations under a comprehensive agreement.
Iranian Foreign Minister Mohammad Javad Zarif said Iran and officials from France, Britain, Germany, the United States, Russia, and China are still "some time away from reaching where we want to be."
He said all UN Security Council resolutions putting sanctions against Iran will be terminated under a comprehensive deal.
A U.S. "fact sheet" issued by U.S. officials said the UN resolutions would be lifted as Iran addresses a list of concerns about its nuclear program.
In remarks from the White House, U.S. President Barack Obama called it a "historic" understanding, saying it was a "good deal, a deal that meets our core objectives." He called it "our best option by far."
But Obama said our "work is not done" on reaching an Iranian nuclear deal and pledged to "always do what is necessary" to stop Iran from getting a nuclear weapon.
U.S. Secretary of State John Kerry tweeted that it was a "big day," saying there was a deal "to resolve major issues on [Iran's] nuclear program" and that all sides would be "back to work soon on a final deal."
British Foreign Secretary Philip Hammond said the preliminary points agreed to are the basis for what could be "a very good deal."
French Foreign Minister Laurent Fabius said there is "still work to do" before a final deal is done.
The U.S. "fact sheet" said Iran has agreed not to build any new nuclear facilities for the purpose of enriching uranium for 15 years.
The U.S. document added that if Iran fails at any point to fulfill its commitments under an agreement, the economic sanctions would "snap back into place." It also said that inspections of Iran's uranium supply chain would last for 25 years after an agreement is signed.
Iran and the six world powers -- who have held talks in the Swiss resort Lausanne for the past eight days -- missed a March 31 deadline to establish a framework agreement.
Western nations want to ensure Iran cannot build a nuclear bomb, while Tehran wants a swift end to UN, U.S., and European Union sanctions that have badly hurt its economy. Iran maintains its nuclear program is for purely peaceful purposes.
Kerry, Zarif, and other negotiators spent all night working on the deal, stopping only at 6 a.m.
Iran Nuclear Negotiations: How We Got Here
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Negotiators were wrangling over the scope of uranium enrichment that Iran would be allowed to conduct, where stockpiles of enriched uranium should be stored, proposed limits on Iran's nuclear research and development, and the timing and conditions for the removal of sanctions.
The five permanent UN Security Council nations and Germany are seeking verifiable curbs on Iran’s nuclear program that ensure Tehran is not able to develop nuclear weapons.
Explainer: Unpacking The Iran Sanctions
Securing a comprehensive deal after more than two decades of tension over Iran's nuclear program would improve the chances of rapprochement between Iran and the United States, whose relations have been badly strained since the Middle East country's 1979 Islamic Revolution.
But conservatives in both the United States and Iran are extremely wary of a deal, as are U.S. allies Israel and Saudi Arabia.
An interim deal was reached in November 2013, but negotiators have missed two self-imposed deadlines for a comprehensive agreement since then.
Israeli Prime Minister Benjamin Netanyahu has repeatedly warned that a deal with Iran could pave its path to the bomb rather than block it.
On April 2, Israeli Intelligence Minister Yuval Steinitz said all options were on the table in the face of the threat of a nuclear-armed Iran.
Speaking to public radio, Steinitz said Israel would seek to counter any threat through diplomacy and intelligence but "if we have no choice...the military option is on the table."
U.S. Defense Secratary Ashton Carter said in an interview earlier this week that if a nuclear deal with Iran is not reached, "the military option certainly will remain on the table."
Iran's defense minister, Brigadier General Hossein Dehghan, said on April 2 that Carter's comments were "designed to affect the rational atmosphere of negotiations" in Lausanne.
Dehghan dismissed Carter's remarks as an "empty" threat that would not affect Iran's "reasonable, rational, and fair position" in the talks, the official IRNA news agency reported.
With reporting Hannah Kaviani of RFE/RL's Radio Farda in Lausanne, AP, and Reuters