Joe Biden received a handwritten letter from Brittany Griner on Monday asking for help in releasing him from a Russian prison.
The White House was informed by Griner's representatives, who also made parts of the letter public.
Griner said that this Fourth of July, the idea of freedom meant something "completely different" to him.
"How the letter got from Griner's prison cell outside Moscow to the White House is a mystery.
Griner, a standout center for the WNBA's Phoenix Mercury, was detained in Russia on February 17 as he tried to enter the Russian Premier League to play for UMMC Ekaterinburg.
She was accused of bringing into Russia illegally manufactured vape cartridges containing hashish oil.
On May 3, U.S. officials designated Griner as "wrongly detained," which indicates that rather than letting her legal case proceed, the U.S. government will attempt to negotiate her release and return.