US President Donald Trump announced Friday that he called off planned strikes on Iran because the expected death toll of 150 people would not have been a "proportionate" response to Tehran shooting down an American drone.
The downing of the drone -- which Iran insists violated its airspace, a claim Washington denies -- has seen tensions between the two countries spike further after a series of attacks on tankers the US has blamed on Tehran.
Under pressure to respond to the high-stakes incident near the strategic Strait of Hormuz, Trump said the US was "cocked & loaded to retaliate" on Thursday night by hitting "3 different sites," but that he scrapped the strikes just 10 minutes before they were carried out.
"I asked, how many will die. 150 people, sir, was the answer from a General," the president tweeted, saying he concluded it would not have been "proportionate to shooting down an unmanned drone." "I am in no hurry, our Military is rebuilt, new, and ready to go," he wrote.
The US president had struck a combative tone in his initial public comments about Iran shooting down the Global Hawk surveillance aircraft.
"Iran made a very big mistake!" he tweeted, later adding at the White House: "This country will not stand for it, that I can tell you."
The US Federal Aviation Administration warned of danger to flights "demonstrated by the Iranian surface-to-air missile shoot-down of a US unmanned aircraft system," and barred American civilian aircraft from the area "until further notice."
The Pentagon says the Global Hawk drone -- one of the most expensive pieces of equipment in the US arsenal, costing over USD 120 million apiece -- was 34 kilometers (21 miles) from Iran when destroyed by a surface-to-air missile in an "unprovoked attack."