Mr. Trump said in September that he would soon ban flavored e-cigarettes to reduce youth vaping, but he has since retreated from that position amid intense lobbying from the vaping industry, conservative anti-tax and anti-regulatory groups.

Instead, the White House held a “listening session” last month in which tobacco and vaping industry officials, along with public health leaders and some elected officials, argued the pros and cons. At the meeting, Mr. Trump said he feared a ban on flavored e-cigarettes would cause an influx of unsafe counterfeit substitutes.

“Any serious solution to skyrocketing rates of youth e-cigarette use must include the removal of kid-friendly flavors, not just the tobacco industry’s preferred policy,” Senator Durbin said in a statement.

A federal survey released earlier this month found that nearly one in three high school students reported using tobacco recently. While e-cigarettes are the most popular product, researchers said that one in three users, or an estimated 2.1 million middle and high school students, also smoked cigars, cigarettes or other tobacco products.

Doctors and public health experts have long been concerned about the effects of nicotine on the teenage brain. The National Academy of Medicine has estimated that 90 percent of adult smokers first start the habit before turning 19, when developing brains are most vulnerable to nicotine addiction. In a 2015 study, the academy reported that banning legal access to those under 21 would spur a 12 percent reduction in tobacco use by the time current teenagers became adults; with the biggest impact among 15-to-17-year olds.

That study was published before Juul and other nicotine e-cigarettes caught on with teenagers. Robin Mermelstein, professor of psychology at the University of Illinois at Chicago, who served on the academy panel overseeing the study, said she expects to see a similar drop in youth use of e-cigarettes once the age limit is raised.

“I think that you would be able to see lots of improvements in reduction of tobacco use among teens, all of which is good because the longer you delay any kind of initiation, the less likelihood there is to develop addiction and the less likely it is that use will escalate,” said Dr. Mermelstein.