LONDON, Feb 12 (Reuters) - A potential U.S. move to block imports of some disposable vapes could cut the booming market for unregulated e-cigarettes by as much as a third, British American ​Tobacco's CEO told Reuters on Thursday, though ‌any impact is unlikely before 2027.

Tobacco giants including BAT and U.S. Marlboro-maker Altria ( MO ) have spent years ⁠fighting a flood of mostly Chinese-made vapes that lack U.S. authorisation ⁠for sale but have still come to dominate the ‌world's largest market ‌for smoking alternatives. 

BAT estimates unregulated devices make up about 70% of U.S. e-cigarette sales, hitting ​both its vape and traditional tobacco businesses. ‌The company has two active cases at the U.S. International Trade Commission, seeking to block imports of unregulated devices. 

Last ​year, an ITC judge ruled in ​BAT's favour ‌in a patent dispute and recommended a general exclusion order that would block disposable vapes infringing its patents. BAT said alongside ⁠annual results on Thursday that it expects a full ITC determination ⁠in March, followed by a 60-day presidential review.    

CEO Tadeu Marroco told Reuters that such a block could have a meaningful impact on the market, which he defined as a drop to below 50% of industry ⁠sales, ‌or by roughly a third. But the scale was ‌hard to predict, he added.

He also warned that a long U.S. supply ⁠chain for such devices and large inventories would delay any effect. "So even if you get the support from the ITC ... it will not be until early next year that you have a material impact on that," he said.

Marroco also said he would not be surprised if the U.S. Food and Drug Administration ​launched a programme to test a different approach to vapes, potentially including flavoured vapes. After years of rejecting most applications for new nicotine products, ​the FDA has looked to speed ‌up or streamline its processes.