Brittney Griner asks fans to write letters to Russia detainee Paul Whelan

(CNN, KYMA/KYMA) - Basketball star Brittney Griner is on a mission to free other Americans who are currently detained in Russia.

On Wednesday, she asked her fans to write letters of support to Paul Whelan, a former U.S. Marine who is still being held in a Russian detention center.

In an Instagram post, Griner said the letters she received while in detention "Helped me to not lose hope"

Early December, the Biden Administration secured Griner's release in a 1-for-1 prisoner swap.

The administration said they haven't been able to secure Whelan's because Russia treats his case differently.

Whelan is currently serving 16 years in prison for espionage charges.

The U.S has referred to the charges as a quote "sham."