However, the official stressed that no decision had been made.

With a two-week ceasefire set to expire, a senior ‌Iranian official said Tehran was “positively reviewing” its participation but no final decision had been made. The comments conveyed a clear change of tone from earlier statements ruling out attendance and pledging to retaliate for US aggression.

The Iranian official said mediator Pakistan was making positive efforts to end the US blockade and ensure Iran’s participation.

The ceasefire had appeared in jeopardy after the US said it had seized an Iranian cargo ship that tried to run its blockade, and Tehran vowed to retaliate.

Iranian Foreign Ministry spokesman ​Esmaeil Baghaei said on Monday that Washington had shown it was “not serious” about pursuing the diplomatic process, and that Tehran would not change its demands.

The US was hoping to start negotiations in Pakistan ​shortly before the ceasefire expires, with sweeping security preparations underway in Islamabad, but Baghaei said the US was “insisting on some unreasonable and unrealistic positions”.

A senior ⁠Iranian source told Reuters that Tehran’s “defensive capabilities”, including its missile programme, were not open to negotiation.

US-IRAN CEASEFIRE SET TO EXPIRE ON TUESDAY NIGHT

A Pakistani security source said Pakistan’s key mediator, Field Marshal Asim Munir, had ​told US President Donald Trump the blockade was an obstacle to talks, and that Trump had promised to consider the advice.

Trump announced the two-week ceasefire with Iran on April 7, and has not specified when precisely it ​ends.

A Pakistani source involved in the talks said it would expire at 8 p.m. EST on Tuesday, which would be midnight GMT or 3:30 a.m. Wednesday in Iran.

Asked over the weekend about the chance of an extension, Trump replied: “I don’t know. Maybe not. Maybe I won’t extend it. But the blockade is going to remain.”

The US has maintained its blockade of Iranian ports, while Iran lifted and then reimposed its own blockade of the Strait of Hormuz, which typically handles roughly one-fifth of ​the world’s oil and liquefied gas supply.