Altria sought Thursday to allay investor concerns that it paid too much for too small a stake in e-cigarette manufacturer Juul.

The tobacco giant in December spent $12.8 billion for a 35 percent stake in Juul, which has dominated the nicotine vaping market and within a few years grown from a small start-up to a $38 billion company. Altria's stake is frozen at 35 percent for the next six years.

The deal gave Altria something its core cigarette business could not: growth. But investors and analysts complained that Altria, the biggest U.S. tobacco company and owner of the best-selling cigarette brand, Marlboro, paid too high a price for too little. Plus, Juul is battling a public relations crisis and facing regulatory uncertainty for fueling what public health officials are calling an e-cigarette epidemic.

Altria CEO Howard Willard tried to ease those concerns Thursday, touting the benefits of the deal on a call with analysts discussing the company's fourth-quarter earnings results. He spent a bulk of his prepared remarks addressing Juul and answered countless questions about the deal.

"When you add to Juul's already substantial capabilities, our underage tobacco prevention expertise and ability to directly connect with adult smokers, we see a compelling future with long-term benefits for both adult tobacco consumers and our shareholders," Willard said.

Juul's revenue grew to more than $1 billion in 2018, up from about $200 million in 2017, Willard told analysts. The actual sales figure last year was about $1.5 billion, people familiar with the matter previously told CNBC. They asked not to be named because the information is confidential.

Willard said the company estimates Juul controls about 34 percent of the total e-cigarette market. Nielsen data has the company's share at more than 75 percent, though that figure only includes convenience stores, not other retailers like vape shops or online stores.

Altria expects vapor volume in the U.S. to grow at a compounded annual rate of 15 percent to 20 percent through 2023, Willard said. Juul is also available in eight markets outside the U.S. while Altria doesn't sell any tobacco products overseas.

Willard said Juul gives Altria a "significant stake in the fast-growing e-vapor category."

Altria's investment comes at a controversial time for Juul. It's been blamed by Food and Drug Administration Commissioner Scott Gottlieb for a surge in teen e-cigarette use, which he's labeling an "epidemic."

Willard said Altria shares the FDA's concerns and the agency's response to youth use is "appropriate and justified." Gottlieb in November said the agency will restrict where flavors can be sold, limiting them to age-restricted stores like vape shops.

"This is an issue that we and others in the industry must continue to address aggressively and promptly," he said. "We understand that the long-term opportunity of tobacco harm reduction is threatened by continued underage use."

He applauded Juul's efforts to curb underage use, including to suspend retail sales of flavored nicotine pods and shut down its social media accounts.

Altria said it intends to file its application for antitrust approval of its Juul investment "shortly."