Officials from the US Embassy in Russia today met Brittney Griner in the Russian prison where she is serving her nine-year sentence for being found with a cannabis e-cigarette refill.

"They could see directly her tenacity and perseverance despite the current circumstances," State Department spokesman Ned Price wrote on Twitter, referring to the meeting between the diplomats and the American basketball champion.

"We continue to lobby for the immediate release of Griner and Paul Whelan and for the fair treatment of every American inmate."

White House spokeswoman Karine Jean-Pierre said the US "made a significant offer to the Russians to resolve the current unacceptable detentions, illicit detentions of US citizens, Brittney Griner and Paul Whelan."