The president says no planes were in the air.

Mr. Trump offered a more detailed version of events later in the day, telling NBC’s Chuck Todd, the host of “Meet the Press,” that he had not given a final go-ahead when military officials checked with him a half-hour before the strikes were scheduled to launch.

“So they came and they said, ‘Sir, we’re ready to go. We’d like a decision.’ I said, ‘I want to know something before you go. How many people will be killed, in this case Iranians?’ ” Mr. Trump told Mr. Todd.

The president said that the officials said they needed to get back to him, but eventually said that “approximately 150” Iranians might die.

Mr. Trump challenged reports that planes were already in the air when he called off the strike, adding: “I didn’t think it was proportionate.”