Strikes on Iran Approved by Trump, Then Abruptly Pulled Back

But in his public appearance, Mr. Trump initially seemed to be looking for a way to avoid a potentially serious military crisis. Instead of directly accusing the leaders of Iran, Mr. Trump said someone “loose and stupid” in Iran was responsible for shooting down the drone.

The president said he suspected it was some individual in Iran who “made a big mistake,” even as Iran had taken responsibility for the strike and asserted that the high-altitude American drone was operating over Iranian air space, which American officials denied.

Mr. Trump said the episode would have been far more serious if the aircraft had been a piloted vehicle, and not a drone. It made “a big, big difference” that an American pilot was not threatened, he told reporters.

Last year, Mr. Trump pulled the United States out of the 2015 nuclear pact with Iran, over the objections of China, Russia and American allies in Europe. He has also imposed punishing economic sanctions on Iran, trying to cut off its already limited access to international trade, including oil sales.

Iran has warned of serious consequences if Europe does not find a way around those sanctions, though it has denied involvement in the attacks on tankers near the vital Strait of Hormuz. On Monday, Iran said it would soon stop abiding by a central component of the nuclear deal, the limit on how much enriched uranium it is allowed to stockpile.

Both Washington and Tehran said the downing of the drone occurred at 4:05 a.m. Thursday in Iran, or 7:35 p.m. Wednesday in Washington. The drone “was shot down by an Iranian surface-to-air missile system while operating in international airspace over the Strait of Hormuz,” the United States Central Command said in a statement. “This was an unprovoked attack on a U.S. surveillance asset in international airspace.”