Olympics: Steven Spielberg has withdrawn from his role as an artistic adviser in this summer's Olympic Games in Beijing over China's lack of progress in resolving the humanitarian crisis in Darfur.
The influential US film director said his conscience would "not allow me to continue with business as usual".
More than 200,000 people have been killed and a further 2.5 million forced from their homes in the five-year conflict between Sudan's Arab-dominated government and Darfur's ethnic African rebels.
Human rights activists have accused China of being partly responsible for Darfur's chaos because of its staunch diplomatic backing of the Sudanese government.
Spielberg's decision could lead others involved in the Games to pull out or reconsider their roles.
In a statement released to trade magazine Variety, Spielberg said: "I find that my conscience will not allow me to continue with business as usual.
"At this point, my time and energy must be spent not on Olympic ceremonies but doing all I can to help bring an end to the unspeakable crimes against humanity that continue to be committed in Darfur.
"Sudan's government bears the bulk of the responsibility for these ongoing crimes, but the international community, and particularly China, should be doing more to end the continuing suffering there.
"China's economic, military and diplomatic ties to the government of Sudan continue to provide it with the opportunity and obligation to press for change."
As the biggest customer for Sudan's oil, China has been the target of Darfur advocates, much to the dismay of Chinese officials who have complained that the Games were being politicised.