Attorneys general in 29 states have called on the federal government, specifically the Food and Drug Administration, to put stronger controls on electronic cigarettes in order to protect young Americans from the risk of nicotine addiction.

In their letter to the FDA, they urged the agency to initiate steps including a ban on television advertising of e-cigarettes and to prohibit the use of fruit and candy flavors making the vapor-producing nicotine delivery devices increasingly popular with young people.

"Imposing federal restrictions on e-cigarettes is an important first step to protect public health from the harmful impacts of tobacco, but more must be done to help keep these products out of the hands of minors," Massachusetts Attorney General Martha Coakley, the letter's co-sponsor, said. "We urge the FDA to take additional steps to help protect youth from becoming addicted to nicotine through these new tobacco products."

Coakley joined with attorneys general in New York, Indiana and Illinois in co-sponsoring the letter, which was then signed by their counterparts in 25 other states.

In an e-cigarette, a liquid containing nicotine is heated and turned into a vapor to be inhaled.

While estimated sales this year could reach $2 billion, a mere fraction of the $100 billion market for traditional cigarettes, e-cigarettes are a fast-growing alternative to traditional tobacco products and are proving especially attractive to younger people.

Proponents of e-cigarettes characterize them as a less dangerous alternative to traditional cigarettes, whose combustion releases a variety of toxins in addition to nicotine.

That's still a matter of debate, opponents say, claiming what isn't up for debate is the potential for e-cigarettes to lead younger users to full-blown nicotine addiction.

Although the FDA has proposed requiring health warnings and banning sales to anyone younger than 18, it has balked at curbing flavored products, advertising or online sales.

The attorneys general, in the letter to the FDA, made it clear the agency's proposal fall short of what they say is needed.

"While we applaud the FDA's proposal to start regulating these tobacco products, it falls far short of what is needed to protect our youth," said New York Attorney General Eric Schneiderman.

The issue has gained urgency as e-cigarettes, with backing and funding by tobacco giants, are increasingly marketed across the United States.

Surveys have shown e-cigarettes are used by as many as 14 million adults in the United States, with an additional 2 million teenagers or children between the ages of 10 and 12 -- dubbed "tweenagers" -- turning to the use of the electronic nicotine devices.