Pakistan's positive and productive endeavors to stop the Middle East conflict are approaching a critical and sensitive stage, Iranian Ambassador to Pakistan Reza Amiri Moghadam said on Tuesday in a social media post.

The statement comes ahead of a deadline set by US President Donald Trump, who has warned Iran it will face "hell" if the Strait of Hormuz is not reopened.

While Moghadam's remarks hinted at progress in ceasefire talks, Iran struck a defiant tone earlier, rejecting a US proposal brokered by Pakistan for an immediate truce and the lifting of its effective blockade of the strait, followed by broader peace talks within 15 to 20 days, Reuters reported, citing a source. 

The Iranian response consisted of 10 clauses, including an end to conflicts in the region, a protocol for safe passage through the Strait of Hormuz, lifting of all sanctions, and reconstruction, official ​IRNA news agency reported. 

On Monday, Trump said "the entire country can be taken out in one night, and that night might be tomorrow night." He vowed to ⁠destroy Iranian power plants and infrastructure if Tehran refused to agree before the deadline.

Without a deal, Trump said "every bridge in Iran will be decimated" by midnight EDT (0400 GMT) on Wednesday and "every power plant in ​Iran will be out of business, burning, exploding, and never to be used again."

Israel, in the meantime, told Iranians to avoid taking trains until 1730 GMT on Tuesday. "Your presence on trains and near railway tracks puts your life in danger," the military wrote on its Persian-language account.

The warning followed reports that Israeli Prime Minister Benjamin Netanyahu had urged Trump not to pursue a ceasefire with Iran at this stage, citing potential risks. Trump, however, said a deal could be reached if Iran meets US demands.

(With input from agencies)