Nuclear program of Iran
U.S. President Obama reportedly sent a letter dated 20 April 2010 to President Lula of Brazil, in which he outlined a proposal of fuel swap. While expressing skepticism that the Iranians would now be willing to accept such a deal, having provided "no credible explanation" for the previous deal's rejection, President Obama wrote "For us, Iran’s agreement to transfer 1,200 kg of Iran’s low enriched uranium (LEU) out of the country would build confidence and reduce regional tensions by substantially reducing Iran’s LEU stockpile." Turkish Prime Minister Recep Tayyip Erdogan received a similar letter. A senior U.S. official told the "Washington Post" that the letter was a response to Iran's desire to ship out its uranium piecemeal, rather than in a single batch, and that during "multiple conversations" U.S. officials made clear that Iran should also cease 20% enrichment; however, the official stated "there was no president-to-president letter laying out those broader concerns".
Joint Comprehensive Plan of Action
A November 2007 U.S. National Intelligence Estimate assessed that Iran "halted its nuclear weapons program" in 2003; that estimate and subsequent U.S. Intelligence Community statements also assessed that the Iranian government at the time had was "keeping open the 'option' to develop nuclear weapons" in the future. A July 2015 Congressional Research Service report said, "statements from the U.S. intelligence community indicate that Iran has the technological and industrial capacity to produce nuclear weapons at some point, but the U.S. government assesses that Tehran has not mastered all of the necessary technologies for building a nuclear weapon."
In March 2013, the United States began a series of secret bilateral talks with Iranian officials in Oman, led by William Joseph Burns and Jake Sullivan on the American side and Ali Asghar Khaji on the Iranian side. In June 2013, Hassan Rouhani was elected president of Iran. Rouhani has been described as "more moderate, pragmatic and willing to negotiate than Ahmadinejad". However, in a 2006 nuclear negotiation with European powers, Rouhani said that Iran had used the negotiations to dupe the Europeans, saying that during the negotiations, Iran managed to master the conversion of uranium yellowcake at Isfahan. The conversion of yellowcake is an important step in the nuclear fuel process. In August 2013, three days after his inauguration, Rouhani called for a resumption of serious negotiations with the P5+1 on the Iranian nuclear program. In September 2013, Obama and Rouhani had a telephone conversation, the first high-level contact between U.S. and Iranian leaders since 1979, and U.S. Secretary of State John Kerry had a meeting with Iranian foreign minister Mohammad Javad Zarif, signaling that the two countries had an opening to cooperation. Former officials alleged that, in order to advance the deal, the Obama administration shielded Hezbollah from the Drug Enforcement Administration's Project Cassandra investigation regarding drug smuggling and from the Central Intelligence Agency. As a result of the Politico report, Attorney General Jeff Sessions ordered an investigation to determine the veracity of the allegations.