Heavily backed by Russian air support and Iranian ground forces, Syria is in a different league than adversaries in other places where the United States is at war. Unlike the Islamic State in various parts of the Middle East, the Taliban in Afghanistan or the Shabab in Somalia, the Syrian government has extensive air defense and missile systems capable of shooting down foreign planes.

Sending bombers and fighter jets, with American or French pilots, to strike Syrian airfields or other facilities is considered risky because it could deepen the conflict if a pilot was shot down. That is why the Pentagon is looking at the same sort of retaliation used last year when two Navy destroyers unleashed a fusillade of 59 Tomahawk cruise missiles at Al Shayrat airfield that was believed to have been used to launch chemical attacks.

But less than 24 hours after that strike, Syrian warplanes were again taking off from the damaged airfield, according to the Syrian Observatory for Human Rights, a monitoring group. Beyond Al Shayrat base, Syria still had numerous others from which it could launch flights. While Mr. Trump’s advisers argued last year that the strike affected Mr. Assad’s calculations, in the end its limited nature ultimately did not thwart the Syrian government’s ability to launch chemical attacks.

“There’s a tension between the desire to do something bigger than last time and the president’s clear desire not to stay engaged in sustained operations,” said Michèle A. Flournoy, an under secretary of defense under President Barack Obama. “Conceivably, they could design a larger one-off strike or a series of smaller strikes.”

“But at the end of the day, it’s sustained pressure on Assad that’s going to change his calculation about whether to use chemical weapons,” Ms. Flournoy said.

David F. Gordon, policy planning director at the State Department under President George W. Bush, said Mr. Trump was almost certainly looking to punish Mr. Assad more severely while limiting American engagement.

“What they’re probably searching for is: What can we destroy that weakens this guy?” Mr. Gordon said. “He has to do more than he did last time, and I think he does want to disrupt their capabilities. But I think it’s basically still the one shot — it may be in two waves or something, but I don’t think there’s an ongoing response to this.”