President Trump says he abruptly canceled a planned military strike on Iran on Thursday night.

He confirmed media reports that he had a last-minute change of heart by saying that the U.S. military was “cocked and loaded” before he changed his mind.

Trump approved U.S. strikes on multiple targets in Iran on Thursday in response to Iran's downing of an unmanned U.S. drone. But he changed his orders at the last minute, in a move first reported by The New York Times.

Explaining his decision Friday morning, Trump wrote: “We were cocked & loaded to retaliate last night on 3 different sights when I asked, how many will die. 150 people, sir, was the answer from a General. 10 minutes before the strike I stopped it, not proportionate to shooting down an unmanned drone.”

He added: “I am in no hurry, our Military is rebuilt, new, and ready to go, by far the best in the world. Sanctions are biting & more added last night. Iran can NEVER have Nuclear Weapons, not against the USA, and not against the WORLD!”

Multiple senior administration officials cited by the Times said military and diplomatic officials were waiting for a strike Thursday evening when the operation was suddenly called off. Planes were reportedly already in the air and ships had gotten into position when the call came down that the operation was not going ahead.

Meanwhile, Iran warned Friday that it had the opportunity to shoot down a U.S. aircraft carrying 35 people that the country claimed was accompanying the drone shot down Thursday. “This plane also entered our airspace and we could have shot it down, but we did not,” said Amirali Hajizadeh, head of the Revolutionary Guards aerospace division.

It’s not immediately clear if there are plans for the strikes to go ahead at a different time. Newsweek cited a Pentagon official as saying U.S. military assets in the region were placed on a 72-hour standby.

The drone incident Thursday was just the latest in a growing list of disputes between Tehran and Washington to raise fears that one simple diplomatic misunderstanding between the two countries could trigger a full-on military confrontation.

Tensions have gotten so high that the Federal Aviation Administration on Friday blocked all American-registered planes from flying over parts of the Middle East, citing “heightened military activities and increased political tensions in the region” that pose “an inadvertent risk to U.S. civil aviation operations.” Other global carriers, including British Airways, KLM, Qantas, and Lufthansa, have followed suit.

It was not immediately clear if the FAA order came in response to news reports about the Trump administration’s planned airstrike, but the agency cited Iran’s shootdown as a reason to fear aircraft could be at risk in the region.

While Trump and his advisers have insisted the U.S. drone was over international waters, Iranian leaders have claimed to have GPS proof that the craft flew into the country’s airspace despite radio warnings.

The attack on the drone also came as many Democratic lawmakers had already begun to question whether the Trump administration was actively trying to build a case for military action against Iran in response to what top officials have described as escalating threats from the country since Trump pulled out of the Obama-era nuclear deal last year.

Just last week, Secretary of State Mike Pompeo backed Trump in blaming Iran for attacks on two fuel tankers in the Gulf of Oman, claiming Tehran was “lashing out” to get back at the U.S. for sanctions.

The Trump administration announced last month that it would be sending additional troops to the Middle East “to send a clear and unmistakable message to the Iranian regime,” as National Security Adviser John Bolton put it at the time.

When reports of the called-off military strikes on Iran broke late Thursday, Democratic lawmakers took to Twitter to sound the alarm over the matter.

“This is governing by chaos. We need a steady hand at the wheel. I stood up against the Iraq War and I know that America cannot afford another disastrous war in the Middle East,” Washington Gov. Jay Inslee, a 2020 candidate, wrote.

Sen. Elizabeth Warren (D-MA), who is also running for president, accused Trump of “instigating” conflict with Iran. “Donald Trump promised to bring our troops home. Instead he has pulled out of a deal that was working and instigated another unnecessary conflict. There is no justification for further escalating this crisis—we need to step back from the brink of war,” she wrote.