Iran on Saturday vowed that it would stand firm against any threats to its borders, and issued a warning to the US and its allies in the region, after US President Donald Trump said the military was “cocked and loaded” to strike against Tehran for downing a US drone on Thursday.

“Firing one bullet towards Iran will set fire to the interests of America and its allies” in the region, armed forces general staff spokesman Brigadier General Abolfazl Shekarchi told the semi-official Tasnim news agency.

“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.

“Regardless of any decision they make… we will not allow any of Iran’s borders to be violated. Iran will firmly confront any aggression or threat by America,” Foreign Ministry spokesman Abbas Mousavi said.

Abbas Mousavi, spokesman for Iran’s Foreign Ministry, gives a press conference in the capital Tehran on May 28, 2019. (Atta Kenare/AFP)

“Iran-controlled airspace over the Persian Gulf and other flight routes are completely safe,” said Iran Civil Aviation Organization spokesperson Reza Jafarzadeh.

On Friday, some of the world’s leading carriers including British Airways, Qantas, Singapore Airlines, Germany’s Lufthansa and Dutch carrier KLM suspended flights over the Strait of Hormuz.

The Federal Aviation Administration warned of a “potential for miscalculation or misidentification” in the region after Iran shot down the US Navy RQ-4A Global Hawk, an unmanned aircraft with a wingspan larger than that a Boeing 737 jetliner.

The downing of the drone — which Washington insists was over international waters but Tehran says was within its airspace — has seen tensions between the two countries spike further after a series of attacks on tankers the US and its staunch ally, Saudi Arabia, have blamed on Iran.

Trump said Friday the US was ready to retaliate against the Islamic Republic but canceled the strikes 10 minutes before they were to be carried out after being told some 150 people could die.

The aborted attack was the closest the US has come to a direct military strike on Iran in the year since the administration pulled out of the 2015 international agreement intended to curb the Iranian nuclear program and launched a campaign of increasing economic pressure against the Islamic Republic.

Trump tweeted Friday that the US was ready to “retaliate last night on 3 different sights when I asked, how many will die.” He said a general told him 150 people, and he canceled the strikes as “not proportionate to shooting down an unmanned drone.”

Trump tweeted that the US will never allow Iran to have a nuclear weapon. But he said he’s in no hurry to respond to the downing of the US drone over the Strait of Hormuz.

He said US sanctions are crippling the Iranian economy and that more are being added.

A US official, who was not authorized to discuss the operation publicly and spoke on condition of anonymity, said the targets would have included radars and missile batteries.

The swift reversal was a reminder of the serious risk of military conflict between US and Iranian forces as the Trump administration combines a “maximum pressure” campaign of economic sanctions with a buildup of American forces in the region. As tensions mounted in recent weeks, there have been growing fears that either side could make a dire miscalculation, leading to war.

Head of the Revolutionary Guard’s aerospace division Brig. Gen. Amir Ali Hajizadeh looks at debris from what the division describes as the US drone which was shot down on Thursday, in Tehran, Iran, Friday, June 21, 2019 (Meghdad Madadi/Tasnim News Agency/via AP)

On Friday, the head of Iran’s Revolutionary Guard’s aerospace division told Iranian state television that Iran had given repeated warnings before launching a missile at the US military surveillance drone.

Gen. Amir Ali Hajizadeh, standing in front of what Iranian authorities described as pieces of the US Navy RQ-4A Global Hawk drone, told state TV that Iranians gave the warnings over radio frequencies that are routinely monitored by drone pilots and the US military. “Unfortunately, they did not answer,” he said.

He also said that Iran could have downed a manned a P-8 American plane, but did not.

Iran collected the debris from its territorial waters, he said. The US military has said that the drone was in international airspace when it was shot down.

However, The New York Times quoted a senior administration official as saying that there was some doubt whether either of the US aircraft did violate Iranian airspace at some point. The official said the doubt was one of the reasons Trump called off the strike, according to the Times, which said that it could under international norms be viewed as an act of war.

The paper also reported that planes were in the air and ships were in position, but no missiles had been fired when word came to stand down.

Trump’s initial comments on the attack were succinct. He declared in a tweet that “Iran made a very big mistake!” But he also suggested that shooting down the drone — which has a wingspan wider than a Boeing 737 — was a foolish error rather than an intentional escalation, suggesting he may have been looking for some way to avoid a crisis.

US Secretary of State Mike Pompeo (C) and National security adviser John Bolton (R) look on as President Donald Trump meets with Canadian Prime Minister Justin Trudeau in the Oval Office of the White House, June 20, 2019. (AP Photo/Evan Vucci)

“I find it hard to believe it was intentional, if you want to know the truth,” Trump said at the White House. “I think that it could have been somebody who was loose and stupid that did it.”

Trump, who has said he wants to avoid war and negotiate with Iran over its nuclear ambitions, cast the shootdown as “a new wrinkle… a new fly in the ointment.” Yet he also said “this country will not stand for it, that I can tell you.”

He said the American drone was unarmed and unmanned and “clearly over international waters.” It would have “made a big, big difference” if someone had been inside, he said.

But fears of open conflict shadowed much of the discourse in Washington. As the day wore on, Trump summoned his top national security advisers and congressional leaders to the White House for an hour-long briefing in the Situation Room. Attendees included Secretary of State Mike Pompeo, national security adviser John Bolton, CIA Director Gina Haspel, Joint Chiefs Chairman Gen. Joseph Dunford, acting Defense Secretary Patrick Shanahan and Army Secretary Mark Esper, whom Trump has said he’ll nominate as Pentagon chief.

Democratic leaders in particular urged the president to work with US allies and stressed the need for caution to avoid any unintended escalation. Senate Democratic leader Chuck Schumer said he told Trump that conflicts have a way of escalating and “we’re worried that he and the administration may bumble into a war.”

Pompeo and Bolton have advocated hardline policies against Iran, but Rep. Adam Schiff, the chairman of the House intelligence committee, said “the president certainly was listening” when congressional leaders at the meeting urged him to be cautious and not escalate the already tense situation.

Some lawmakers insisted the White House must consult with Congress before taking any actions.