VIENNA -- Advanced planning is underway for a major announcement by world powers and Iran detailing the outcome of their nuclear talks, after an 18-day marathon effort.Several Western diplomats confirmed just before midnight local time that the governments of Britain, France, Russia, China, Germany, the United States and Iran were finally preparing for the event.No delegation has confirmed that the deal is complete, and meetings over its text continued late into the evening. One plenary among world powers first began eight minutes past midnight here. And just hours before, the White House said that some issues remain unresolved in the talks. "There continue to be significant issues that remain," White House press secretary Josh Earnest told reporters, adding: "Nothing is agreed to until everything is agreed to."But Iranian delegates told their press corps not to go to sleep tonight, and European officials have echoed the same.If announced, a deal would cap a two-year diplomatic effort with the aim of ending international concerns over Iran's nuclear work. World powers, including Israel, believe that Iran's nuclear program has been military in nature since 2002.Tehran denies this charge, and asserts that its nuclear program is entirely peaceful. Because it claims a right to nuclear power, the five permanent members of the United Nations Security Council and Germany have been negotiating a deal with Iran that will respect its right to a nuclear program so long as it receives verifiable assurances that it remains exclusively peaceful.On April 2 in Lausanne, Switzerland, the seven nations agreed on a political deal that was meant to frame the agreement.A deal announced in the early hours of Tuesday morning would have to be submitted within five calendar days, in full, to the United States Congress. US President Barack Obama would have to verify that the deal "meets United States non-proliferation objectives, does not jeopardize the common defense and security" and "provides an adequate framework to ensure that Iran’s nuclear activities permitted thereunder will not be inimical to or constitute an unreasonable risk to the common defense and security" of the US. Congress will then have a 60-day period to review and vote on the agreement.Sending a message on Twitter on Monday that he quickly deleted, Iranian President Hassan Rouhani said that a comprehensive nuclear deal "is the victory of diplomacy and mutual respect over the outdated paradigm of exclusion and coercion. And this is a good beginning."Israel opposes the deal in its current form.