WASHINGTON - Negotiations amongst world powers and Iran over its nuclear program, now at a key stage geared toward achieving a comprehensive diplomatic solution to the crisis, will be kept largely private by the parties involved for the next four months, the United States said on Friday.Calling the talks "sensitive," State Department deputy spokeswoman Marie Harf said that the parties have together agreed not to divulge details of the issues laid on the negotiating table.Those issues were codified in a framework agreement settled on this week in Vienna by Iran and the P5+1 powers - the US, United Kingdom, France, Russia, China and Germany."We're not going to get into any specific issues that we discussed," Harf said, confirming that a framework had been set, and that all future talks would take place in Vienna."We really do think that in this sensitive and detailed and complicated negotiation, we can’t do that publicly and we need to do that privately, even discussing the issues."The next round of talks will take on March 17, but the parties will be in "constant contact" through the interim period, she added.Harf spoke to journalists on the phone from Jerusalem, where she traveled with Wendy Sherman, US Under Secretary of State for Political Affairs and America's lead negotiator with Iran.Sherman was in Israel briefing Prime Minister Binyamin Netanyahu on Friday on the progress of the negotiations. "Suffice it to say, all of our concerns must be met," Harf said, when asked by The Jerusalem Post whether the closure of Iran's mountain-burrowed nuclear facility in Fordo, and the dismantling of its vast infrastructure of centrifuges, were determined by Iran as legitimate topics of negotiation.Leading up to talks in Vienna this past week, Iranian officials said they would not entertain closing "any facilities" in its nuclear program.