President Joe Biden on Thursday called a Russian court's sentencing of US basketball star Brittney Griner to nine years in prison "unacceptable."

"Russia is wrongfully detaining Brittney. It's unacceptable and I call on Russia to release her immediately so she can be with her wife, loved ones, friends and teammates," Biden said in a statement.

Griner, 31, was convicted of smuggling and possessing "a significant amount of narcotics," said judge Anna Sotnikova.

The WNBA, the US professional women's basketball league, blasted the conviction and sentence of one of its leading stars.

"Today's verdict is unjustified and unfortunate, but not unexpected," said WNBA Commissioner Cathy Englebert in a joint statement with NBA Commissioner Adam Silver.

"The WNBA and NBA's commitment to her safe return has not wavered," they said, adding that they hoped that the sentencing would open the door for her return to the United States.

The six-foot-nine (2.06 meters) star was detained at a Moscow airport in February after she was found carrying vape cartridges with cannabis oil in her luggage. The arrest came just days before Moscow launched its military intervention in Ukraine.

The US president reiterated that he would "work tirelessly and pursue every possible avenue" to repatriate Griner and another detained American in Russian, Paul Whelan.
Negotiations are reportedly underway to swap the two for Russians incarcerated in the United States, including the notorious arms smuggler Viktor Bout.

In a separate statement US Secretary of State Antony Blinken said the case placed a spotlight on "the Russian government's use of wrongful detentions to advance its own agenda, using individuals as political pawns."

"Russia, and any country engaging in wrongful detention, represents a threat to the safety of everyone traveling, working, and living abroad," Blinken said.