President Donald Trump said Friday the United States was “cocked & loaded” to strike Iran but pulled back at the last minute because it 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 countries spike 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 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.”

Qantas changes flight paths amid US-Iran row

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.

The Wall Street Journal reports that US officials confirmed a future military response also hasn’t been ruled out.

Deputy foreign minister Abbas Araghchi told Swiss ambassador, Markus Leitner, whose country represents US interests in Iran, of the evidence on Thursday night, the foreign ministry.

“Even some parts of the drone’s wreckage have been retrieved from Iran”s territorial waters,” Araghchi told the Swiss envoy.”

On Friday, US President Donald Trump tweeted his logic behind the decision.

He already declared “Iran made a very big mistake!” after it was shot down in international airspace near the Persian Gulf and refused to rule out going to war with the Islamic nation.

“You’ll find out,” Mr Trump responded when asked whether the US would respond to the attack or go to war with Iran.

“Obviously, you know, we’re not going to be talking too much about it. You’ll find out. They made a very big mistake.

“Probably Iran made a mistake. I would imagine it was a general or somebody who made a mistake in shooting that drone down.

“I find it hard to believe it was intentional. I think it could’ve been somebody that was loose and stupid. It was a very foolish move, that I can tell you.”

He denied that his advisers were pushing him to start a war with Iran.

“No, not at all. Not at all. In fact in many cases it’s the opposite,” he said. “Look, I said I want to get out of these endless wars. I campaigned on that. I want to get out.

“This is a new fly in the ointment, what happened shooting down the drone. And this country will not stand for it, that I can tell you.”

The incident has left the Trump White House confronting dramatically increased tensions with Iran, which has declared it is ready for war.

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.

Trump and Saudi Crown Prince Mohammed bin Salman on Friday discussed the “threat” posed by Tehran, and the US requested a UN Security Council meeting on Iran on Monday.

The New York Post reports that Iran’s Revolutionary Guard said it had shot down an “intruding American spy drone” after it entered into the country’s territory.

Relations between Iran and the US have soured since America announced it would send 1000 more troops to the region after Washington said Tehran was involved in attacking two oil tankers.

According to CNN, Mr Trump has sought to calm nerves within his administration and continues to privately express wariness at wading into another foreign conflict.

“Don’t worry about a thing,” Trump told Fox News. “Everything’s under control.”

Iran said the Revolutionary Guard took down the drone, claiming it flew into Iranian territory — an account hotly disputed by American officials, who say the aircraft was operating in international airspace over the Strait of Hormuz.

“Iranian reports that the aircraft was over Iran are false,” US Central Command spokesman Navy Captain Bill Urban said. “This was an unprovoked attack on a US surveillance asset in international airspace.”

Revolutionary Guard Major General Hossein Salami warned that Iran is “totally ready and prepared for war.”

“The downing of the American drone is an open, clear and categorical message, which is: the defenders of the borders of Iran will decisively deal with any foreign aggression,” Maj Gen Salami said. “This is the way the Iranian nation deals with its enemies.”

Following the drone downing, United Airlines announced it would suspend flights between New Jersey’s Newark airport and India’s financial hub, Mumbai.

“Given current events in Iran, we have conducted a thorough safety and security review of our India service through Iranian airspace and decided to suspend our service,” United said on its website.

The airline did not say how long the suspension would last.

The Department of Defence announced it would send 1,000 more troops to the region after the US said Tehran was involved in attacking two oil tankers.

In 2018, President Trump pulled the US out of the Iran nuclear deal which was struck in 2015 with the Islamic republic and the US, UK, Russia, France, China and Germany in an effort to limit Iran’s nuclear development in exchange for the lifting of economic sanctions.

The deal was a prized foreign policy win for former US President Barack Obama. But since he began his campaign for the 2016 presidential election, Mr Trump has derided the deal as weak and declared it would not stop Iran from obtaining nuclear weapons.

In the past 12 months, the US has imposed much harsher sanctions on Iran and the Islamic nation’s economy has declined sharply as a result.

Iran threatened this week to violate the nuclear agreement, saying that by the end of June it will have stockpiled more nuclear fuel than was permitted under the international agreement.

It also flagged the possibility that it could begin the enrichment nuclear fuel to higher levels than what it needs for nuclear power plants - raising fears Iran is moving to build nuclear weapons.