The two-time Olympic gold medallist and eight-time Women's National Basketball Association (WNBA) All-Star was arrested in February at an airport outside Moscow for carrying vape cartridges containing hashish oil in her luggage.

Griner's fans and fellow athletes mounted a campaign for her release and sent letters of support as she was subsequently convicted of drug smuggling and transferred to one of Russia’s most notorious penal colonies.

"Thanks to the efforts of many, including you, I am home after nearly 10 months," Griner wrote in a letter posted on her Instagram account.

"Your letters helped me to not lose hope during a time where I was full of regret and vulnerable in ways I could have never imagined."

US officials said they had pressed for the release of both Griner and Whelan, who is being held on what Washington called "sham" espionage charges, but that the Griner swap with arms dealer Viktor Bout was a "one or none" deal as Moscow was treating Whelan's case differently.

Whelan expressed dismay that more was not done to secure his release and Republican lawmakers were critical of Democratic President Joe Biden, who said the United States would not give up on securing his freedom.

Griner said the letters she received showed the "power of collective hands".

"There remain too many families with loved ones wrongfully detained," wrote Griner, who left the Brooke Army Medical Center last week and said she intends to resume her career in the WNBA next season.

"I hope you'll join me in writing to Paul Whelan and continuing to advocate for other Americans to be rescued and returned to their families," she added.