Walmart will increase the minimum age to buy tobacco products to 21 starting July 1, joining the growing list of retailers boosting their age policies, the company said in a letter to the Food and Drug Administration.

Walmart said it is also in the process of discontinuing sales of fruit and dessert-flavored e-cigarettes. The retailer outlined steps to prevent minors from buying tobacco products in a letter to the FDA.

The FDA in April threatened to fine Walmart, Kroger, Family Dollar and more than a half dozen convenience store chains for illegally selling tobacco products to minors. Walmart had a violation rate of about 17%, the FDA said at the time. 

Walmart said it would take a number of steps, including to strengthen its disciplinary action when stores fail secret shopper checks, enhance its data, analytics and systems, and upgrade its age-verification training by using virtual reality technology.

"We unequivocally acknowledge that even a single sale of tobacco product to a minor is one too many, and we take seriously our responsibilities in this regard," John Scudder, Walmart's U.S. chief ethics and compliance officer, wrote in the letter Wednesday. 

Walgreens and Rite Aid have already announced they would raise the minimum age to buy tobacco products. Rite Aid also said it would stop selling all e-cigarettes in its stores though it would continue to sell cigarettes. A dozen states have already increased their age requirements and federal lawmakers are also considering nationwide legislation.

Read the full letter here.