President Donald Trump has revealed that the US military was “cocked and loaded to retaliate” against Iran, but he changed his mind 10 minutes before planned strikes.

The president said he had called off strikes after being told 150 people would die.

Donald Trump tweeted: “10 minutes before the strike I stopped it, not proportionate to shooting down an unmanned drone.”

Attacks on three sites were planned in response to the shooting down of a US unmanned drone this week.

The late reversal was first reported by the New York Times on June 20. The newspaper said the operation had been “in its early stages” when President Trump stood the US military down.

On June 21, President Trump said: “I am in no hurry.”

“Our military is rebuilt, new, and ready to go, by far the best in the world.”

The president said Iran had downed the drone on June 17, despite an earlier US military statement that the incident happened at 23:35 GMT on June 19 (04:05 Iran time on June 20).

On June 21, President Trump told NBC News that he decided not to give final approval to the planned strikes because of the predicted death toll.

He said: “I didn’t like it. I didn’t think it was proportionate.”

Tehran says the unmanned US aircraft entered Iranian airspace early on June 20. The US maintains it was shot down in international airspace.

Tensions have been escalating between the two states, with the US recently blaming Iran for attacks on oil tankers operating in the region.

Iran has announced it will soon exceed international agreed limits on its nuclear program.

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“Iran can NEVER have nuclear weapons,” President Trump said in his tweets on the aborted strikes – also revealing that increased economic sanctions against Iran were “added last night”.

The US has now asked the UN Security Council to meet on June 24 to discuss Iran, Reuters reports.

In its initial report, The New York Times said that as late as 19:00 local time on June 20, US military and diplomatic officials had still expected the strikes to take place on agreed targets, including Iranian radar and missile batteries.

However, President Trump refuted this report on June 21, telling NBC that no planes were in the air.

The strikes had been set to take place just before dawn on June 21 to minimize risk to the Iranian military or to civilians, the New York Times report added.

Tweeting on June 21, President Trump said three sites had been targeted.

Meanwhile, the Associated Press quoted a US official as saying the strikes had been recommended by the Pentagon and had been among options presented to senior administration officials.

According to the New York Times, top Pentagon officials warned a military response could result in a spiraling escalation with risks for US forces in the region.

The operation was called off after President Trump spent most of day on June 20 discussing Iran with his national security advisers and congressional leaders, AP reports.

Secretary of State Mike Pompeo and National Security Advisor John Bolton had pushed for a hard-line stance, but congressional leaders urged caution, the agency says.

Separately, Reuters quoted two Iranian officials as saying Tehran had received a message from President Trump through Oman overnight warning about an imminent US attack.

That report was later denied by a spokesman for Iran’s National Security Council, who said there was no truth to it and no message was sent.

In the US, Democratic House Speaker Nancy Pelosi said America had no appetite for war with Iran, while the leading candidate for the Democratic presidential nomination, Joe Biden, called President Trump’s Iran strategy a “self-inflicted disaster”.

Russian President Vladimir Putin said a war would be a “catastrophe with unpredictable consequences”.

UN Secretary General Antonio Guterres urged all parties to exercise maximum restraint.

On June 20, the FAA issued an emergency order prohibiting US airlines from operating in an overwater area of Tehran-controlled airspace nearby in response.

Airlines from other countries, as KLM, Emirates, British Airways and Qantas, have also said they will re-route their flights to avoid parts of Iran.