Images made public of the women's kit, showing a very high-cut pantyline, triggered criticism from several athletes for what they saw as a decision to prioritise skimpiness over function.
"They are absolutely not made for performance," US steeplechaser Colleen Quigley said in a message to Reuters.
Debate has raged for years over more revealing outfits for women Olympians in disciplines from beach volleyball to gymnastics, and some rules on competition wear are changing.
Germany's women's gymnastics team wore full-length bodysuits at the Tokyo Olympics, in what they said was a stand against sexualisation in the sport. Gymnastics New Zealand this month updated its attire rules to allow women and girls to wear shorts or leggings over their leotards.
Nike said in an email to Reuters that it was offering athletes unitard options with both a brief and a short for this Olympics, whereas it only offered the brief for the Tokyo Olympics.
Nike's track and field kits for men and women include nearly 50 apparel pieces and 12 competition styles for specific events, the brand said when launching the outfits.
Nike-sponsored pole vaulter Katie Moon, in a post on X, said the kit was "concerning", but added that women athletes were given many options on what to wear, and that she preferred briefs to shorts.
A spokesperson for USA Track & Field said: "Athlete options and choices were the driving force for USATF in the planning process with Nike."
US middle-distance runner Athing Mu and US sprinter Sha'Carri Richardson were among the athletes modelling Nike's Olympic kits at the launch show in Paris. While Mu wore briefs, Richardson wore a version of the outfit with shorts.
Quigley said Nike should also offer athletes who make the team custom tailoring to ensure the kit fits perfectly.
"Our bodies are all different and it seems silly to expect us to compete at the highest level of our sport without a properly fit uniform," she said.
Nike told Reuters it will have tailors available for Olympic and Paralympic athletes this year.
