Reading out a joint statement, European Union foreign policy chief Federica Mogherini hailed what she called a "decisive step" after more than a decade of work. Iranian Foreign Minister Mohammad Javad Zarif followed with the same statement in Farsi.
Mogherini said the seven nations would now start writing the text of a final accord, based on the agreed upon framework deal. She cited several agreed-upon restrictions on Iran's enrichment of material that can be used either for energy production or in nuclear warheads. She said Iran won't produce weapons-grade plutonium.
She added that the final-status deal, which was given a self-imposed deadline of June 30, will include endorsement from the UN Security Council.
The time that it would take for Iran to acquire enough fissile material for one weapon is currently assessed to be 2 to 3 months. That timeline will be extended to at least one year, for a duration of at least ten years, under the framework agreement.
For the next 15 years, Iran has agreed not to build any new facilities for the purpose of enriching uranium, and to reduce its current stockpile of some 10,000 kilograms of low-enriched uranium to 300 kilograms. Tehran has also agreed not to enrich uranium over 3.67 percent for at least 15 years.
Tehran will reduce its installed centrifuges by approximately two-thirds - from 19,000 centrifuges to only 6,104 centrifuges installed in the Natanz facility, and only 5,060 of them will be enriching uranium for the next 10 years. All 6,104 centrifuges will be IR-1s, Iran’s first-generation centrifuge.
The more advanced centrifuges - of the 2, IR-4, IR-5, IR-6, or IR-8 models - will not be used for uranium enrichment for at least 10 years and will be placed in IAEA-monitored storage, along with any excess centrifuges and enrichment infrastructure. These excesses will be used only as replacements for operating centrifuges and equipment. International inspectors will continue supervising Iran's uranium supply chain for the next 25 years.
Under the terms of the agreement, uranium enrichment will stop at the Fordow site for at least 15 years. No research and development associated with uranium enrichment will be conducted at Fordow for 15 years. Instead, Fordow will be converted into a nuclear, physics, technology, research center. Iran has also agreed not to keep fissile material in Fordow for the next 15 years.
The deal also calls for an international joint venture to assist Iran in building and redesigning a modernized heavy water reactor at Arak.
In return, following the signing of the final-status deal, the US and EU will suspend nuclear-related sanctions placed on Iran - but only after the IAEA verifies that Iran has taken all of the key steps agreed upon in the framework deal. According to the deal, if at any time Iran fails to fulfill its commitments, the sanctions will be put back into place.
All past UN Security Council resolutions on the Iran nuclear issue will be lifted simultaneous with the completion, by Iran, of nuclear-related actions addressing all key concerns (enrichment, Fordow, Arak, PMD, and transparency). However, core provisions in the UN Security Council resolutions – those that deal with transfers of sensitive technologies and activities – will be re-established by a new UN Security Council resolution that will endorse the deal and urge its full implementation.
Secretary of State John Kerry tweeted there was a deal "to resolve major issues on nuclear program. Back to work soon on a final deal."
The US and five other countries hope to curb Iran's nuclear technologies that could be used to make weapons. Tehran denies such ambitions but is negotiating because it wants a lifting of economic sanctions imposed over its nuclear program.
Despite the optimism following the press conference in Lausanne, Zarif said that reaching a nuclear deal with the six major powers will not mean normalizing of ties with its longtime foe the United States.
"Iran and US relations have nothing to do with this, which was an attempt to resolve the nuclear issue ... We have serious differences with the United States," he said.
"We have built mutual distrust in the past.. .So what I hope is that through courageous implementation of this some of that trust could be remedied. But that is for us all to wait and see."
Talks in the Swiss city resumed several hours after a flurry of overnight sessions between Kerry and Zarif, and other meetings involving the six powers.
The talks – the latest in more than a decade of diplomatic efforts to curb Iran's nuclear prowess – hit the weeklong mark on Thursday, shortly before the State Department announced they would go into double overtime from the March 31 deadline for a political framework.
As the sides bore down on efforts to get a deal, German Foreign Minister Frank-Walter Steinmeier canceled a planned visit to Lithuania, Estonia and Latvia. French Foreign Minister Laurent Fabius was also back, less than a day after leaving the city.
Reuters and the Associated Press contributed to this report.