Most Americans, even those who smoke, favor raising the tobacco-purchasing age to 21.

Seven in 10 cigarette smokers support banning the sale of tobacco products to anyone under age 21, according to a survey by the Centers for Disease Control and Prevention. Three out of four Americans overall favor the policy, the poll found.

Hawaii is currently the only state where people must be 21 to buy tobacco products, although a handful of cities and counties have passed such laws. Most states set the age threshold at 18, except for Alabama, Alaska, New Jersey and Utah, where the legal age is 19.

If all states raised the legal purchasing age to 21, smoking would drop by 12 percent and there would be nearly 250,000 fewer premature deaths due to cigarette use, according to an Institute of Medicine report released in March. Just 25 percent of respondents to the CDC poll opposed such measures.

Smoking rates in the U.S. have dramatically dropped over the last few decades, as the CDC has led a massive anti-smoking campaign and states and localities have placed stricter limits on where people can smoke in public places. But health advocates remain concerned about smoking among teens, as the vast majority of adult smokers first try cigarettes before age 21.

"Raising the minimum age of sale to 21 could benefit the health of Americans in several ways," said Brian King, acting deputy director for Research Translation in CDC's Office on Smoking and Health. "It could delay the age of first experimenting with tobacco, reducing the likelihood of transitioning to regular use and increasing the likelihood that those who do become regular users can quit."

Data for the study came from Styles, a national online survey of adults aged 18 and older.