"I find that my conscience will not allow me to continue business as usual," Spielberg said in a statement issued on a day when Nobel Peace laureates sent a letter to China's president urging a change in policies toward its ally Sudan.

"At this point, my time and energy must be spent not on Olympic ceremonies, but on doing all I can to help bring an end to the unspeakable crimes against humanity that continue to be committed in Darfur," he added.

China is a leading oil customer and supplier of weapons to Sudan and is accused by critics of providing diplomatic cover for Khartoum as it stonewalls international efforts to send peacekeepers into Darfur.

In April, Spielberg wrote a letter to Chinese President Hu Jintao adding his voice to the chorus of people who have protested China's involvement with the Sudanese government over the crisis in Darfur.