The U.S. Food and Drug Administration (FDA) plans to meet top-level executives of e-cigarette makers, the agency's chief said on Thursday, hinting that some companies seem to be backing away from commitments related to youth's access to e-cigarettes.

"There's no reason manufacturers must wait for FDA to forcefully address the epidemic. Yet some already appear to back away from commitments made to the FDA and the public," FDA Commissioner Scott Gottlieb said on Twitter.

@SGottliebFDA The #FDA continues to conduct our own inquiries and/or investigations of e-cig makers related to marketing activities and other product-related issues. I'll be reaching out to CEOs to schedule new meetings. Manufacturers and management are accountable for the youth epidemic. 5/5

In November, the FDA announced sweeping restrictions on flavored tobacco products, including electronic cigarettes popular among teenagers, and restricting sale of fruity or sweet flavors at retail outlets.

Tobacco giant Altria and Juul Labs, among other e-cigarette makers, have said that they supported efforts to limit access to e-cigarettes.

In a rare move last week, the U.S. Surgeon General Jerome Adams issued an advisory urging aggressive steps against e-cigarette use among teens, which he said has become an "epidemic".