A Russian bobsledder who tested positive for a banned substance at the Pyeongchang Olympics has admitted doping and been disqualified from the games.

The Court of Arbitration for Sport says Nadezhda Sergeeva has accepted a provisional suspension but reserves the right ''to seek the elimination or reduction'' of her expected ban from the sport.

Sergeeva, who wore a T-shirt at the start of the games that said ''I don't do doping,'' was the second Russian to test positive at the Olympics. She placed 12th in her event. Curler Alexander Krushelnitsky also tested positive and returned his bronze medal from the mixed doubles competition.

The Russian delegation said in a statement that the substance Sergeeva tested positive for was trimetazidine, a medication used to treat angina. It affects metabolism and is banned by the World Anti-Doping Agency.

Russian athletes are competing under the Olympic flag rather than their own and wearing neutral uniforms after the country's national federation was suspended for operating a doping scheme at the 2014 Sochi Games.

Russia is waiting to hear if the International Olympic Committee will end the suspension and allow the country to march under its flag at Sunday's closing ceremony.