"Firing one bullet towards Iran will set fire to the interests of America and its allies", armed forces general staff spokesman Brigadier General Abolfazl Shekarchi told the Tasnim news agency.
"Today, the situation in the region is to Iran’s advantage.
"If the enemy - especially America and its allies in the region - make the military mistake of shooting the powder keg on which America's interests lie, the region will be set on fire," Shekarchi warned.
President Donald Trump said Friday that the United States was "cocked & loaded" to strike Iran but pulled back at the last minute as it would not have been a "proportionate" response to Tehran's shooting down of an unmanned US drone.
Watch: Trump says, 'not looking for war with Iran'
The downing of the drone - which Tehran insists violated its airspace, a claim Washington denies - has seen tensions between the two countries spike after a series of attacks on oil tankers the US has blamed on Iran.
Under pressure to respond to the high-stakes incident near the strategic Strait of Hormuz, Trump said the US was prepared to hit "3 different sites" Thursday night but that he scrapped the strikes "10 minutes" before they were to have been launched.
"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."
According to excerpts of an interview with NBC's "Meet the Press" conducted Friday morning at the White House, Trump said he had not given final approval to strikes against Iran, and that no planes were in the air.
"But they would have been pretty soon. And things would have happened to a point where you wouldn't turn back or couldn't turn back," he said, adding that he did not want war with Iran, but if it came to pass, there would be "obliteration like you've never seen before."
The US president had struck a combative tone in initial comments Thursday about Iran shooting down the Global Hawk surveillance aircraft, but as the pre-dawn incident whipped up fears of open conflict, Trump moved to dial back tensions.
Iran vowed Friday to defend its borders after downing the drone, with the commander of the aerospace arm of its elite Revolutionary Guards saying the aircraft was warned twice before it was engaged over the Gulf of Oman.
And it denied a report that Trump had warned it via Oman of an impending attack unless it was willing to negotiate.
The US special representative on Iran, Brian Hook, accused Tehran of rejecting diplomatic overtures to deescalate regional tensions.
"Iran needs to meet diplomacy with diplomacy, not military force," Hook told reporters in Saudi Arabia.
President Donald Trump said Friday that the United States was 'cocked & loaded' to strike Iran but pulled back at the last minute as it would not have been a 'proportionate' response to Tehran's shooting down of an unmanned US drone.