President Donald Trump posted on social media on Saturday the deal with Iran was scheduled to be signed the next day, his 80th birthday.
Pakistani Prime Minister Shehbaz Sharif said the two sides had agreed on a framework for a peace deal and that Islamabad was preparing for an electronic signing on Sunday, to be followed by technical-level talks in the coming week.
"We are closer to a peace deal than ever before," he said on X.
But Iran did not confirm a Sunday signing. Iranian Foreign Ministry spokesperson Esmaeil Baghaei, speaking before Trump's post, had cautioned against commenting on the timing of the signing but was quoted by state media saying, "It will not be tomorrow," but could happen "in the coming days".
Trump wrote on Truth Social that after a framework deal is signed, the Strait of Hormuz, a vital artery for global oil supplies that Iran has blocked, would immediately be "open to all".
While US bombings have heavily degraded Iran's military-industrial base and damaged its military, experts say the war has left hardline Revolutionary Guard dominance more firmly entrenched than before.
Videos on social media and Iranian news websites showed opponents of an agreement gathering in squares and in front of the Foreign Ministry in Tehran, appearing to blame Iranian Foreign Minister Abbas Araqchi as they chanted, "Araqchi have some shame, let go of America!"
When the US and Israel launched the war against Iran on February 28, Trump called on Iranians to rise up and take over state institutions.
Even as the US and Iran appeared to be moving toward an agreement over the past two days, clashes have continued, as the US military imposes a blockade on Iran and seeks to loosen Iran's chokehold on the Strait of Hormuz, which was the conduit for 20 per cent of the world's oil shipments before the war.
Early on Saturday, US forces shot down multiple Iranian one-way attack drones heading toward the strait, the US military said.
Israel, which says it is not a party to the US-Iran deal, said on Saturday that it had struck more than 70 sites over a 24-hour period in Lebanon against Iranian ally Hezbollah.
Israeli Prime Minister Benjamin Netanyahu has clashed with Trump over US demands that Israel curb military action in Lebanon to allow Washington to reach a deal with Tehran.
On Friday, Araqchi said that while changes in the deal were still possible, the tentative agreement showed his country had emerged stronger from the conflict.
At pro-government rallies held across Iran on Saturday night, residents and news agencies reported that hardliners opposed to the framework agreement loudly voiced their dissatisfaction.
The proposed memorandum of understanding calls for reopening the strait and lifting the US naval blockade, sources on all sides of the talks said. Negotiations over Iran's nuclear program - a key rationale Trump has given for the war - would take place afterwards.
"Iran is going to open up the Strait of Hormuz, that's a requirement. It could be open with no tolls. As they do that, we will lift our blockade," a US official told reporters.
"It's going to happen in conjunction, and part of the next step, the phase after that, is going to be the demining of the straits," the official said, indicating countries in the G7 major powers could play a role.
Draft terms described to Reuters by multiple sources indicate the US would begin releasing billions of dollars in frozen Iranian assets and waive sanctions on its oil exports, in return for Iran opening the strait.
Iran's Fars news agency quoted Baghaei as saying the release of Iran's frozen assets was an integral part of the agreement and also that Iran would have to charge for services in the Strait of Hormuz.
He said foreign military bases in the region must end, the agency reported, without providing details.
Iran's nuclear program would be addressed during a 60-day period of talks. A US official said the agreement would ultimately lead to the dismantling of Iran's nuclear program, with its stockpile of highly enriched uranium to be destroyed and removed.
