Iran's Supreme Leader Mojtaba Khamenei has instructed that the country's stockpile of near-weapons-grade uranium should not be sent outside the country, two senior Iranian sources told news agency Reuters. The move hardens Tehran's position on one of the key demands made by the United States during peace talks.

Pakistan army chief Asim Munir is reportedly set to enter the ceasefire efforts, a development that comes after Iran said on Wednesday that it was reviewing a new US proposal aimed at ending the Middle East conflict, while President Donald Trump described the negotiations as being on the "borderline" between reaching an agreement and renewed military action as the conflict, under a temporary truce, neared the three-month mark.

Trump, who earlier said the talks were in their "final stages," later cautioned that diplomatic efforts could collapse rapidly.

"It's right on the borderline, believe me," AFP news agency quoted Trump telling reporters at Joint Base Andrews near Washington. "If we don't get the right answers, it goes very quickly. We're all ready to go."