How Mr. Trump sees the killing of General Suleimani as advancing his broader agenda on Iran is unclear, and on Friday he seemed to portray the operation as something of a one-off: a necessary step to ensure that tensions between the United States and Iran do not spiral out of control. General Suleimani was plotting “imminent and sinister attacks” before “we caught him in the act and terminated him,” the president said from his resort in Palm Beach, Fla., although administration officials did not describe any threats that were different from what they said the general had been orchestrating for years.

“We took action last night to stop a war. We did not take action to start a war,” Mr. Trump said. The president’s decision to kill the general at this time appeared to many military experts as a potentially reckless escalation. But his policy toward Iran, what administration officials call a “maximum pressure” campaign, has long underestimated how the country would respond to economic sanctions that have crippled its economy.

When Iranian operatives blew holes in oil tankers in the Gulf of Oman in June and launched drone strikes on Saudi oil facilities in September, Mr. Trump opted in both cases against a direct, immediate military response. Still, one day after the drone strike targeting General Suleimani, the Pentagon announced it was sending around 3,000 more troops to Kuwait as a precaution against growing threats to American forces in the region.

Lindsay P. Cohn, a professor of political science at the Naval War College, said that Mr. Trump appears to be convinced that General Suleimani’s death will not lead to a significant surge of violence in the Middle East. It satisfies two imperatives for him: appearing to look tough without taking on, at least for now, any new commitments.

“He doesn’t want to get entangled. But he doesn’t want to look weak,” said Professor Cohn, adding that her opinions did not necessarily represent those of the Defense Department.

The president’s mercurial approach to Iran has left a trail of alienated allies — including European NATO allies angry about his decision to withdraw from the 2015 Iran nuclear deal and Arab nations in the Persian Gulf region uncertain about Mr. Trump’s resolve to support them in the face of direct attack from Iran.