The International Olympic Committee warned that a refusal by any participant in next month's Games to compete against an athlete from a particular country is against the IOC's Code of Ethics.
The warning came Thursday in response to an Algerian kayaker who withdrew last month from a World Cup event after learning that he would be competing against an Israeli.
“Refusing to participate in an Olympic event because of a fellow athlete/team’s religion or nationality would not only be unsporting behavior but a serious breach of the IOC’s Code of Ethics, the principles of the Olympic Charter and the Athletes Oath,” IOC spokesman Emanuelle Moreau said in a statement.
Moreau advised athletes who object to competing against participants from other countries to "stay at home."
Following the World Cup incident, the head of the Algerian Olympic committee told the Times of London that all Algerian Olympic competitors may refuse to compete against Israelis at the London Olympics in July.
“There is an obligation to ask our government if we have to meet Israel in sport,” Rachid Hanifi told the paper last week.
Athletes from Arab states and Iran have boycotted Israeli athletes at recent Olympics.