A Russian court on Tuesday rejected an appeal by the US basketball star Brittney Griner against her nine-year prison term on drug charges, ignoring her plea for the "traumatic" sentence to be reduced.

The court in Krasnogorsk near Moscow ruled to leave Griner's August verdict "without change", while noting that each day the athlete had spent behind bars since her February arrest would be counted as one-and-a-half days of her term.

Griner had earlier pleaded for the sentence to be cut at Tuesday's hearing, which Washington denounced as a "sham".

"I really hope that the court will adjust this sentence because it has been very very stressful and very traumatic," Griner said by video link from her detention centre just outside the Russian capital.

The 32-year-old was handed nine years in prison in August for possessing vape cartridges with a small quantity of cannabis oil, after she was arrested at a Moscow airport in February.

The case came amid fierce tensions between Moscow and Washington over Russia's military offensive in Ukraine.

Speaking slowly so her words could be translated into Russian, Griner asked the court for leniency given that the amount of cannabis found was "barely over the significant amount".

"I don't understand the first court's decision to give one year less than the max when I've been here almost eight months and people with more severe crimes have gotten less than what I was given," she said.

"So I just beg that the court... reassess my sentence."

Her lawyers had earlier said that Griner "does not expect any miracles" but had hoped for a reduction of her term.

White House Press Secretary Karine Jean-Pierre earlier this month described the appeal hearing as "another sham judicial proceeding" and said Griner should be released immediately.

When she was arrested, the two-time Olympic basketball gold medallist and Women's NBA champion had been in Russia to play for the professional Yekaterinburg team, during her off-season from the Phoenix Mercury.

She pleaded guilty to the charges, but said she did not intend to break the law or use the banned substance in Russia.

Griner had testified that she had permission from a US doctor to use medicinal cannabis to relieve pain from her many injuries, and had never failed a drug test.

The use of medical marijuana is not allowed in Russia. (AFP)