Two-time basketball Olympic champion Brittney Griner, who has been imprisoned in Moscow, is being unfairly detained by Russia, according to a new assessment by the US government.
A spokeswoman for the State Department in Washington confirmed corresponding US media reports on Tuesday.
She called the security of American citizens "one of the highest priorities of the US government".
The spokeswoman also said that US President Joe Biden's special representative for hostage matters, Roger Carstens, would take care of the US citizen's case from now on.
"The U.S. government will continue to make efforts to provide Ms. Griner with appropriate assistance."
On March 23, a US diplomat was granted consular access to Griner.
The US State Department had previously urged consular care.
After her arrest on charges of drug possession, Griner is in custody at Moscow's Sheremetyevo Airport.
Griner was arrested at Moscow Airport after vape cartridges containing cannabis oil were allegedly found in her luggage.
A court in the Moscow region in the city of Khimki had extended the arrest until May 19.
The professional basketball league WNBA also focused more attention on the case on Tuesday.
In the season starting next weekend, a logo with the initials BG and Griner's shirt number 42 should be visible on all pitches.
"We continue to work to bring Brittney home and are grateful for the support the basketball community has shown to BG and her family during this exceptionally challenging time," said WNBA President Cathy Engelbert.
So far, the WNBA had held back with public actions.
Reportedly, this was done out of concern for making things worse for Griner.
The Phoenix Mercury, with which she lost to Chicago Sky in the championship final last season, can continue to pay Griner in full, without this money being counted in the squad's salary cap.