The Food and Drug Administration on Thursday put off a long-anticipated ruling on whether Juul Labs and other major e-cigarette companies could continue to sell their products in the United States.

The companies are at the center of a review of the vaping industry that the agency has been conducting for the past year. The F.D.A. said on Thursday that it had so far denied the applications of 946,000 flavored e-cigarette products to remain on the market, mostly made by small companies. No e-cigarettes have been approved through the application process, an agency official said.