The two-time Olympic gold medallist was arrested on Feb. 17 at a Moscow airport with vape cartridges containing cannabis oil, which is banned in Russia. She was sentenced on Aug. 4 to nine years in a penal colony on charges of possessing and smuggling drugs.

Griner's lawyers, Maria Blagovolina and Alexander Boykov, said she would take part in Tuesday's hearing by video link from the detention centre where she has been held, and that they expected a verdict the same day.

"She is very nervous waiting for the appeal hearing. Brittney does not expect any miracles to happen but hopes that the appeal court will hear the arguments of the defense and reduce the term," they said.

Griner pleaded guilty at her trial but said she had made an "honest mistake" and not meant to break the law.

Washington says Griner was wrongfully detained and has offered to exchange her for Viktor Bout, a Russian arms dealer serving a 25-year prison sentence in the United States.

Moscow has also suggested it is open to a prisoner swap.

Bill Richardson, a former U.S. ambassador to the United Nations who travelled to Moscow in September, has said he believes Griner and former U.S. Marine Paul Whelan could both be released by the end of the year. A U.S. consular officer spoke briefly on the phone with both detainees last Tuesday.