ReutersUS President Donald Trump said both "both sides must take their time" to get a deal "right"US President Donald Trump has instructed his negotiators "not to rush into a deal" with Iran, after reports suggested an agreement was close.
According to US media reports, the deal under discussion involves a 60-day ceasefire extension, reopening the Strait of Hormuz and further negotiations over Iran's nuclear programme.
In a social media post, Trump said "constructive" talks were proceeding but "both sides must take their time and get it right".
Trump said on Saturday an agreement had been "largely negotiated", prompting speculation an announcement could be imminent.
But reports in Iranian media say there are still "one or two" points of disagreement in the potential deal.
Iranian officials had also signalled progress in talks over the weekend, but foreign ministry spokesperson Esmail Baghaei said that did not mean agreements would be reached on key issues.
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Israel and the US launched massive air strikes on Iran on 28 February. Tehran retaliated by firing drones and missiles at Israel and US targets in countries across the Gulf.
A ceasefire agreed in April meant to facilitate talks has largely been observed, despite occasional exchanges of fire.
In Sunday's post on Truth Social, Trump said negotiations "are proceeding in an orderly and constructive manner, and I have informed my representatives not to rush into a deal in that time is on our side".
"Both sides must take their time and get it right. There can be no mistakes!"
Trump also said Iran "must understand" it cannot develop a nuclear weapon, a stance he has frequently reiterated and that is shared by Israel and other Western allies.
The US and its allies suspect that Iran is seeking to develop a nuclear weapon by enriching uranium - but Tehran has said its nuclear programme is solely for peaceful purposes.
In his social media post, the US president also said Washington's blockade of Iranian ports - which has been in place since early April - will remain "in full force and effect until an agreement is reached, certified, and signed".
The US has been enforcing its blockade to exert pressure on Tehran to agree to its terms.
For its part, Iran has continued to control the Strait of Hormuz, effectively closing the vital waterway through which around 20% of the world's oil and liquefied natural gas travels. The move has sent oil prices soaring globally.
US Secretary of State Marco Rubio earlier said that "significant" but "not final" progress had been made in the negotiations.
He hinted at good news on Hormuz, saying that progress over the past 48 hours - if it works - could result in a "completely open strait... without tolls".
On Saturday, Baghaei told state television that Iran was in the process of finalising a "memorandum of understanding" which would allow additional talks so that "ultimately a final agreement can be reached".
Trump also mentioned a "memorandum of understanding" in a Truth Social post on Saturday.
Pakistan's Deputy Prime Minister Ishaq Dar, who has been mediating talks, has said that recent negotiations are "grounds for optimism" that a positive outcome is "within reach".
Some US media outlets reported that no agreement between the two countries was expected to be signed on Sunday, citing officials.
