The details of the draft deal, which is still being negotiated, are broadly in line with an interim agreement clinched on April 2 in Lausanne, Switzerland. But as negotiations reached a critical stage, new details emerged, and it was significant that the latest draft included inspections for military sites, access to experts and a proposed timeline for putting a possible deal in place.  The information from the source was preliminary and subject to change because it was based on a draft of the nuclear deal that was not the final version and that could be amended before final approval by Iran and the six powers.  Read MoreAs Iran deal looms, is it time to worry about oil?  Diplomats close to the talks say that they are hoping to approve a final version of the draft document as early as Tuesday. Negotiations were continuing in the early hours of Tuesday to reach an agreement, the diplomats said.  Read MoreNow we can focus on terrorism and Tehran: Italy PM  The source said that Iran and the U.N. International Atomic Energy Agency have agreed on a plan to address outstanding questions about the possible military dimensions of past Iranian nuclear activity by the end of this year, adding that some sanctions relief would be conditioned on Tehran resolving this issue.  Read MoreIran deal would face tough battle in Congress  The plan agreed by the IAEA and Iran includes one visit to the Parchin military site as well as possible interviews with Iranian nuclear scientists, the source noted.  Read MoreBanks, retail sales, Iran may steal the thunder from Greece  Nuclear negotiations between Tehran and six world powers missed a midnight deadline on Monday to reach a final deal, but diplomats from all sides said they hoped for a breakthrough in the coming hours.
A draft nuclear deal between Iran and six major powers calls for U.N. access to all suspect Iranian sites, including military sites, a sources said.