Iranian state TV said a ceasefire with the United States in force since April 8 would expire at 3:30 am Wednesday, Tehran time (0000 GMT Tuesday).
The timing is consistent with when the 14-day truce went into effect, though US President Donald Trump recently said it would end a day later, on Wednesday evening Washington time.
Mediator Pakistan had said earlier in the day that the ceasefire would expire at 2350 GMT on Tuesday.
"Ceasefire ends at 4:50 am PST, 22 April," Information Minister Attaullah Tarar posted on X, referring to Pakistan Standard Time.
Trump had given the Wednesday evening end date in comments to Bloomberg, and said it was "highly unlikely" he would agree to extend the truce.
Pakistan has invited the warring sides to a second round of talks in Islamabad, but Iran has yet to formally respond, Tarar said.
He added that a decision by Tehran was "critical" before the truce expired.
Shortly thereafter, Iranian foreign ministry spokesman Esmaeil Baqaei said a final decision on participating still hadn't been made.
"The reason for this is not indecision; the reason for this situation is that we are faced with contradictory messages, contradictory behaviours, and unacceptable actions from the American side," he said.
