"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.

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.