They found overweight people with high blood pressure who drank one less sugar-laden beverage a day significantly lowered their blood pressure over 18 months.
For most Americans this means cutting soft drink intake in half.
"We found if you lower your consumption of sugary drinks, it may help you reduce your blood pressure," said Dr. Liwei Chen of Louisiana State University Health Science Center, whose findings appear in the journal Circulation.
"If you reduce your consumption by two servings, you would probably lower your blood pressure even more," Chen said in a telephone interview.
The study adds to mounting pressure on U.S. food and beverage companies as newly passed health reform legislation shifts the nation's focus on ways to prevent disease as well as treat it.
Too much sugar not only makes people fatter, but is also a key culprit in diabetes, heart disease and stroke, according to the American Heart Association.
Several states, including New York and California, have weighed a tax on sweetened soft drinks to defray the cost of treating obesity-related diseases.
A report by the U.S. Institute of Medicine in February declared high blood pressure a "neglected disease" in the United States, accounting for one in six deaths and adding $73 billion a year in health costs.
Chen's study looked specifically at the effect of sugar intake on blood pressure. The team used data on 810 adults aged 25 to 79 with borderline high blood pressure -- readings of 120/80 to 139/89 -- and stage I hypertension -- readings of 140/90 and 159/99
At the start of the study, people drank 10.5 ounces (310 ml), or roughly one serving, of sweetened beverages a day. They included drinks sweetened with sugar or high-fructose corn syrup such as soft drinks, fruit drinks and lemonade.
After 18 months, average consumption had fallen by half a serving, and both the systolic blood pressure -- the "top number" blood pressure reading when the heart beats -- and diastolic blood pressure -- the "bottom number" reading between beats -- had fallen significantly.
They said drinking one less soft drink a day resulted in a 1.8 millimeters of mercury drop in systolic pressure and cut diastolic pressure by 1.1 millimeters of mercury.
"Weight loss is part of the reason but not all," Chen said, noting that even after controlling for that, the improvement in blood pressure was statistically significant.
She said American adults drink an average of 2.3 servings (28 ounces/828 ml) of sugar-sweetened beverages per day.
The American Beverage Association says sugar-sweetened drinks do not pose any particular health risk, and are not a unique risk factor for obesity or heart disease.