as concerns over the mosquito-borne virus mount following the first cases of local transmission in the continental United States.
There is no approved vaccine or drug for Zika, a virus spreading rapidly in the Americas that can cause the birth defect microcephaly, marked by small head size that can lead to severe developmental problems in babies.
A number of companies and academic groups are racing to develop a Zika vaccine, which is not expected to be ready for widespread use for at least two to three years.
The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health federal research agency, said its early-stage clinical trial will involve at least 80 healthy volunteers ages 18 to 35 at three study sites.
It said the trial will evaluate the experimental vaccine's safety and ability to elicit an immune system response.
"A safe and effective vaccine to prevent Zika virus infection and the devastating birth defects it causes is a public health imperative," NIAID Director Dr Anthony Fauci said in a statement.
US vaccine maker Inovio Pharmaceuticals in June won US Food and Drug Administration approval to begin testing its Zika vaccine in humans.
It began its clinical trial last month, aiming to enroll 40 healthy adult volunteers in Miami, Philadelphia and Quebec City.
US concerns over Zika, which is spreading rapidly in the Americas and has hit Brazil the hardest, have increased since Florida authorities last week reported the first signs of local transmission of the virus in a Miami neighbourhood. Public health officials have said small, localised outbreaks are likely in southern US states already vulnerable to mosquito-borne disease.
The White House said President Barack Obama spoke by telephone to Florida Governor Rick Scott about the Zika outbreak.
Texas health officials said on Wednesday that they were on high alert for local Zika transmission and urged residents to follow precautions against mosquito bites.
"It's the perfect mix - local transmission in Florida, travel to Brazil, and we're at the height of mosquito season in Texas," said John Hellerstedt, Texas Department of State Health Services commissioner, referring to the Olympic Games beginning this week in Rio.
Fauci said that while it will "take some time" before a vaccine against Zika is commercially available, the launch of the study marked an important step forward.
The study sites for the NIH vaccine trial were: NIH facilities in Bethesda, Maryland; the University of Maryland School of Medicine in Baltimore; and Emory University in Atlanta.
The NIAID said the vaccine approach is similar to one used for another vaccine it developed for West Nile virus. The Zika vaccine includes a piece of DNA that has been engineered to contain genes for proteins of the Zika virus. Such DNA vaccines do not contain infectious material so they cannot cause a person to become infected with Zika, the NIAID said.
