Nigeria, April 7 -- Iran has flatly rejected an American ceasefire proposal and issued its own list of counter-demands, even as US President Donald Trump threatens to unleash devastating strikes on Iranian infrastructure if no agreement is reached by Tuesday evening.

There is no sign of an imminent deal.

Mr Trump himself described Tehran's response to Washington's ceasefire offer as "significant" but ultimately "not good enough," leaving both sides locked in a dangerous standoff with no clear resolution in sight.

The American president has set an 8 pm Eastern Time deadline on Tuesday for Iran to reopen the Strait of Hormuz, though his deadlines have shifted at least three times in the past three weeks.

If no agreement is reached, Mr T...