“Symbolic politics at its worst,” said Robert Malley, the president and chief executive of the International Crisis Group and a former senior Obama administration official on the Middle East. “At every level it is illogical, counterproductive or useless.”

Treasury Secretary Steven Mnuchin said the administration would add Mohammad Javad Zarif, Iran’s foreign minister and its top negotiator on the nuclear deal, to the sanctions list this week. (In his announcement about the sanctions on the supreme leader, Mr. Trump misspoke and said “Ayatollah Khomeini,” who died in 1989, rather than “Khamenei.”)

The inflation rate in Iran has risen to about 50 percent and many Iranians are dissatisfied with the economy, but authoritarian leaders have historically shown they can withstand stress from sanctions for many years. Some Iranian citizens also blame the United States government for the devastation of their economy, and they point to the shortage of critical medicine, even though Trump administration officials say they do not intend to limit humanitarian aid.

Iranian officials could choose to carry out nonfatal attacks on United States or international interests, as they did with the downing of the drone, to try to get the Trump administration to ease sanctions. Iran’s naval commander, Rear Adm. Hossein Khanzadi, said on Monday that the military was capable of shooting down other drones that violate Iranian airspace.

Mr. Trump said on Monday that he was willing to negotiate with Iran — “I think Iran, potentially, has a phenomenal future” — but insisted Iranian leaders would have to end their pursuit of nuclear weapons, as well as halt uranium enrichment, “fueling of foreign conflicts” and “belligerent acts directed against the United States and its allies.”

Mr. Trump always emphasizes the need to prevent Iran from getting a nuclear weapon, while his hawkish top foreign policy aides, Secretary of State Mike Pompeo and John R. Bolton, the national security adviser, say Iran must also make wholesale changes to its policies in the Middle East.