President Donald Trump said he called off a strike against Iran because the estimated casualties were not “proportionate to shooting down an unmanned drone.”

“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.” Trump tweeted Friday morning.

The New York Times first reported Thursday that Trump was going to move ahead with strikes against Iran, after the Islamic Revolutionary Guard Corps shot down a U.S. Navy RQ-4 Global Hawk surveillance drone. The Times also reported that senior administration officials said Trump ultimately canceled the strikes.

“10 minutes before the strike I stopped it, not proportionate to shooting down an unmanned drone,” Trump said Friday. “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!”

Iran had an opportunity to target manned aircraft, according to Press TV, a state-run news outlet in Iran. Iran reportedly refused to strike a P-8 surveillance aircraft with a manned crew that was flying near the Global Hawk.

“We are aware of the IRGC statement being made," a U.S. defense official said in a statement. "All attacks violate international law and represent a clear threat to international freedom of navigation and freedom of commerce.”

Tensions between the U.S. and Iran have escalated in recent weeks, and the two countries are at odds over whether the unmanned surveillance drone shot down Thursday was flying over Iran.

Lt. Gen. Joseph Guastella, commander of U.S. Air Forces Central Command, told reporters Thursday that the drone was shot down as it was flying over the Gulf of Oman and the Strait of Hormuz during a surveillance mission and fell into international waters. Reporters were provided a map of where the U.S. claims it was shot.

But Iran claims the drone was flying over Iran, and the head of the Islamic Revolutionary Guard Corps said later that “borders are our redline, and any enemy violating these borders will not go back.”

“The downing of the US drone had an explicit, decisive and clear message that defenders of the Islamic Iran’s borders will show decisive and knockout reactions to aggression against this territory by any alien,” Maj. Gen. Hossein Salami said, according to Tasnim News Agency.

He said Iran didn’t want to instigate war with the U.S., but noted it was prepared to defend itself.