The United States and five other world powers announced a landmark accord Sunday morning that would temporarily freeze Iran’s nuclear program and lay the foundation for a more sweeping agreement.
It was the first time in nearly a decade, American officials said, that an international agreement had been reached to halt much of Iran’s nuclear program and roll some elements of it back.
The aim of the accord, which is to last six months, is to give international negotiators time to pursue a more comprehensive pact that would ratchet back much of Iran’s nuclear program and ensure that it could be used only for peaceful purposes. […]
Iran, which has long resisted international monitoring efforts and built clandestine nuclear facilities, agreed to stop enriching uranium beyond 5 percent, a level that would be sufficient for energy production but that would require further enrichment for bomb-making. To make good on that pledge, Iran will dismantle links between networks of centrifuges.
Its stockpile of uranium enriched to 20 percent, a short hop from weapons-grade fuel, would be diluted or converted into oxide so that it could not be readily used for military purposes. Iran agreed that it would not install any new centrifuges, start up any that are not already operating or build new enrichment facilities.
The agreement, however, does not require Iran to stop enriching uranium to a low level of 3.5 percent, or to dismantle any of its existing centrifuges.