The US is banning the sale of all products sold by Juul, one of the country's top e-cigarette companies.
The Food and Drug Administration (FDA) said it did not have enough data to be sure that marketing the firm's products was "appropriate for the protection of public health".
Juul said it would challenge the move.
It comes after other recent anti-smoking efforts by the FDA, including plans to reduce the amount of addictive nicotine allowed in cigarettes.
The agency had already barred the fruity flavours that helped make Juul a phenomenon among teenagers a few years ago.
"Today's action is further progress on the FDA's commitment to ensuring that all e-cigarette and electronic nicotine delivery system products currently being marketed to consumers meet our public health standards," FDA commissioner Robert M. Califf said in a statement.
Juul, founded in California in 2015 by a pair of former smokers, has promoted its vaping pods as a healthier alternative to traditional tobacco cigarettes.
But the products, which contain high concentrations of nicotine, raised alarm as use among teens exploded, with more than quarter of high schoolers using e-cigarettes in 2019, according to a federal survey.
In 2020 the FDA said it would require companies to submit their e-cigarette products for approval. It has since granted some of them a green light.
In its statement, the FDA said it had not received any information to suggest an "immediate hazard".
But it also noted the major role Juul, whose products under review had nicotine levels of 3% and 5%, still plays in the market.
"We recognise these make up a significant part of the available products and many have played a disproportionate role in the rise in youth vaping," Mr Califf said.
Juul said it would seek a stay of the ruling, which would allow it to keep selling as it explores options including an appeal.
"We respectfully disagree with the FDA's findings and decision and continue to believe we have provided sufficient information and data based on high-quality research to address all issues raised by the agency," the firm's chief regulatory officer, Joe Murillo, said in a statement.
"We intend to seek a stay and are exploring all of our options under the FDA's regulations and the law, including appealing the decision and engaging with our regulator.
"We remain committed to doing all in our power to continue serving the millions of American adult smokers who have successfully used our products to transition away from combustible cigarettes, which remain available on market shelves nationwide," he added.
Juul has already seen its business hit by regulatory action, as officials investigated its marketing practices to teens and tightened rules on what flavours could be sold. International restrictions have also limited its expansion outside the US.
Altria Group, which took a 35% stake in the company in 2018 for more than $12bn, has been forced to write off much of the value of its investment.
The firm's shares sank 9% on Wednesday, after the Wall Street Journal reported plans for the ban.