“We are aware of the reported social media posts and the (Department of Defense) department is reviewing the matter,” said Pentagon spokeswoman Sabrina Singh.
A CIA spokeswoman said the agency was also aware of the post and was investigating the claims.
A document posted on social media states that 16,000 to 17,500 Russian soldiers have been killed since Russia’s invasion of Ukraine on 24 February 2022.
Officials have said that the United States believes the real figure is much higher, with about 200,000 Russians killed and wounded.
Ukrainian forces turned back Russia’s initial advance on Kiev in early 2022, and the conflict, which Moscow calls a “special military operation”, has become one of grinding trench warfare in the east and south.