The Food and Drug Administration on Thursday issued a long-awaited proposal to ban menthol cigarettes and flavored cigars, a major victory for anti-smoking advocates but one that could dent sales at tobacco companies.

The proposal, which comes a year after the agency announced the plan, still needs to be finalized and can take years to implement as it is likely to face stiff opposition from the tobacco industry.

“The proposed rules would help prevent children from becoming the next generation of smokers and help adult smokers quit,” said Health and Human Services Secretary Xavier Becerra

For decades, menthol cigarettes have been in the crosshairs of anti-smoking groups who have argued that they contribute to disproportionate health burdens on Black communities and play a role in luring young people into smoking.

Menthol cigarettes, banned in many states including California and Massachusetts, account for more than a third of the industry’s overall market share in the United States, even as overall smoking rates have been declining in the country.

Shares of Altria Group, British America Tobacco, and Imperial Brands were mixed in late morning trading.

The FDA said the public would have the opportunity to submit either electronic or written comments directly to the dockets on the proposed rules through July 5.

Once all the comments have been reviewed and considered, the FDA will decide whether to issue final product standards.