U.S. and Iranian negotiators have reached an agreement on a 60-day memorandum of understanding to extend the ceasefire and launch negotiations on Iran's nuclear program, but President Trump has yet to give his final approval, two U.S. officials and a regional source involved in the mediation efforts tell Axios. Iran has also not confirmed its acceptance.Why it matters: The signing of the MOU would be the most significant diplomatic breakthrough since the war started, but a final agreement that tackles Trump's nuclear demands would still require further intensive negotiations."This is an agreement to get everybody to the table. We will work out the details in the negotiations," one of the U.S. officials saidBehind the scenes: U.S. officials said terms of the deal were mostly agreed to as of Tuesday, but both sides still needed approval from senior leadership.The U.S. officials claimed the Iranians later came back and said they had the necessary approvals and were prepared to sign. Iran has not confirmed that.The U.S. negotiators briefed Trump on the details of the final deal, but he did not immediately sign off. "The president relayed to the mediators that he wants a couple of days to think about it," a U.S. official said.Flashback: Trump and his advisers thought they were close to a deal several times at earlier stages in the war, but talked repeatedly stalled.Zoom in: The U.S. officials said the 60-day MOU will state that shipping through the Strait of Hormuz will be "unrestricted." A U.S. official said this means no tolls and no harassment and that Iran will have to remove all mines from the strait within 30 days.The U.S. naval blockade will also be lifted, but that will happen in proportion to the restoration of commercial shipping, a U.S. official said.The MOU will include an Iranian commitment not to pursue a nuclear weapon, the officials said. It will also state that the first issues to be negotiated during the 60-day window will be how to dispose of Iran's highly enriched uranium and how to address Iranian enrichment.The U.S. will commit to discuss sanctions relief and the release of frozen Iranian funds as part of the negotiations. The MOU will also include a discussion of a mechanism to help Iran start receiving goods and humanitarian aid. Split screen: Even as the negotiations were being finalized, the U.S. and Iran had two skirmishes in the Strait of Hormuz in the past 48 hours.What they're saying: A U.S. official claimed Iran now has a chance to unshackle its economy and "there are people in their system that understand that it is an opportunity to go in a different direction," adding: "We will find out during the 60-day negotiations if that's the case."The U.S. officials claimed there will be no side deals or secret clauses about sanctions relief or funds going to Iran. "The more the Iranians are willing to give the more they will get," one said.The two U.S. officials claimed the Iranians had given verbal commitments during the negotiations about their willingness to make nuclear concessions, but "we will not know until we get in the room, which is why we want to do this MOU. It gets both sides into the room to negotiate directly."The MOU also refers to promoting "regional peace," and the Trump administration hopes to have discussions about Iran's support for regional proxies, the officials said.The officials said that if it becomes clear during the negotiations that Iran is unable to deliver on the nuclear issue, Trump will have all options on the table — economic and military. The withdrawal of U.S. forces sent to the region is subject to a final agreement, they said.What to watch: Tehran has not confirmed its acceptance of the MOU. Trump also said on Wednesday that he was not in a rush.Go deeper: What's in the dealThis is a developing story and has been updated throughout.