US President Donald Trump speaks during a cabinet meeting in the Cabinet Room of the White House on May 27.

A tentative agreement has been reached in talks between the United States and Iran, US officials said Thursday, though President Donald Trump hasn’t signed off on it and the situation in the region remained tense.

Trump’s approval will be key to any agreement, officials cautioned, and the president said a day earlier he wasn’t satisfied with the current state of talks. It also wasn’t clear whether Iran’s supreme leader had given his sign-off, believed to be another necessary step toward ending the conflict.

Still, the finalization of text between the two nations was a sign that diplomacy was proceeding, despite active hostilities between the US and Iran over the past 48 hours.

The memorandum of understanding would include language lifting constraints on the Strait of Hormuz, allowing unrestricted navigation by vessels and lifting a US blockade.

It would start a 60-day negotiation period to address Iran’s nuclear program, including the fate of its stockpile of highly enriched uranium. Sources said the most difficult issues related to Iran’s nuclear program still have to be worked out as part of those talks.

Trump has appeared optimistic previously about an agreement with Iran, only to later change course.

US sources all cautioned that any advancements in the talks could be upended quickly if Trump decides to withhold his approval.

He has been under pressure from members of his own party, along with Prime Minister Benjamin Netanyahu of Israel, to reject a deal that would ease pressure on Iran.

Trump has been seeking advice to ensure the deal is strong enough, one person familiar with the matter said. He has been fixated on ensuring the deal can be marketed as stronger than the 2015 Obama-era nuclear deal from which he withdrew during his first term.

Iran’s semi-official Tasnim News Agency, citing unnamed sources close to the negotiating team, reported that the text of the agreement “has not yet been finalized or made definitive.” The sources added that Iran has not yet informed the Pakistani mediator that the text is finalized.