Iranian Deputy Foreign Minister Abbas Araghchi later told state television about $4.2 billion in seized oil revenue would be released under the deal. Senior officials in the Obama administration put the total at $7 billion.
Under the November agreement, Iran agreed to limit its uranium enrichment to 5 percent the grade commonly used to power reactors. The deal also commits Iran to stop producing 20 percent enriched uranium which is only a step away from weapons-grade material and to neutralize its 20 percent stockpile over the six months.
In exchange, economic sanctions Iran faces would be eased for six months. During that time, the so-called P5+1 world powers Britain, China, France, Germany, Russia and the United States would continue negotiations with Iran on a permanent deal.
The West fears Iran's nuclear program could allow it to build a nuclear bomb. Iran says its program is for peaceful purposes, such as medical research and power generation. Iran's semi-official ISNA news agency reported Sunday that under the terms of the deal, Iran will guarantee that it won't try to attain nuclear arms "under any circumstance." But Araghchi stressed Iran could resume production of 20 percent uranium in "one day" if it chose.
The senior U.S. officials said U.N. inspectors would have daily access to Iranian nuclear sites and would make monthly reports. Iran will dilute half of its nuclear material during the first three months of the agreement, the officials said, and all of it by the end of the agreement.
In exchange, Iran would have access to parts for its civilian aviation, petrochemical and automotive industries, as well as be allowed to import and export gold, the officials said. The deal also gives Iran access to international humanitarian and medical supplies, though Iran still could not use U.S. banks and the majority of sanctions would remain in place, they said.
The senior U.S. officials spoke on the condition of anonymity.
European Union negotiator Catherine Ashton praised the deal in a statement, saying "the foundations for a coherent, robust and smooth implementation ... have been laid."
German Foreign Minister Frank-Walter Steinmeier called the deal "a decisive step forward which we can build on."
U.S. Secretary of State John Kerry welcomed the deal, saying further negotiations "represent the best chance we have to resolve this critical national security issue peacefully and durably."
In a statement, Obama said the deal "will advance our goal of preventing Iran from obtaining a nuclear weapon."
"I have no illusions about how hard it will be to achieve this objective, but for the sake of our national security and the peace and security of the world, now is the time to give diplomacy a chance to succeed," Obama said.