Saudi Arabia's female judo competitor Wojdan Shaherkani has been banned from wearing the hijab -- a headscarf -- during her matches at the London Olympics.
The International Judo Federation said Shaherkani, 18, should step onto the mat "according to the principle" of judo with her head uncovered.
Judo applies strict safety rules and any covering on the head is deemed to present a risk to the fighter's health.
Shaherkani is part of a two-member women's team that Saudi Arabia is sending to an Olympics for the first time.
American-raised runner Sarah Attar is the second woman in the Saudi squad.
Saudi authorities allowed them to compete after the International Olympic Committee and right groups exerted intense pressure for an end of the kingdom's practice of sending all-male teams to the games.
Based on reporting by AFP and AP