"US Central Command has no indication that any New Syrian Forces fighters have defected to Al Nusra Front, contrary to several press and social media reports," CENTCOM said in a press release on Wednesday.
The US-led coalition of 62 nations has trained, or plans to train, Syrian fighters as part of a program to combat the Islamic State.
CENTCOM said approximately 70 participants in the train-and-equip program had returned to Syria from a training camp in Turkey over the weekend.
"[They] are currently operating there as New Syrian Forces," the press release explained. CENTCOM added that the fighters remain in control of all weapons and equipment issued by the coalition against the Islamic State.