"As the primary economic, military and political partner of the Government of Sudan, and as a permanent member of the United Nations Security Council, China has both the opportunity and the responsibility to contribute to a just peace in Darfur," said the letter.

"Ongoing failure to rise to this responsibility amounts, in our view, to support for a government that continues to carry out atrocities against its own people," said the letter, released on a day of events by the Save Darfur Coalition.

The letter was signed by Nobel Peace laureates Bishop Carlos Belo, Shirin Ebadi, Adolfo Perez Esquivel, Rigoberta Menchu, Archbishop Desmond Tutu, Elie Wiesel, Betty Williams and Jody Williams. Other signatories included Western politicians, former Olympic athletes and entertainers, including actress Mia Farrow.

Farrow and the coalition have mounted a global campaign for China to change its policies in Sudan. Beijing sells weapons to the Sudanese government and buys oil from it.

In more than four years of conflict in Sudan's western region of Darfur, 200,000 people have died and 2.5 million have been driven from their homes, according to estimates from international experts. Khartoum says 9,000 people have died.

The letter to Hu acknowledged Chinese support for a U.N. Security Council Resolution calling for the deployment of a U.N.-African Union peacekeeping force to Darfur and other diplomatic efforts.

"However, we note with dismay that the Chinese government worked to weaken the resolution before it passed," it said. The letter said China doubled its trade with Sudan in 2007 and continued its military relationship with the African country.

The Save Darfur Coalition said it will stage protests in Senegal, Nigeria, France, Italy, Australia and other countries on Tuesday.

The Washington protest will feature a mock ceremony near China's Embassy, in which Chinese officials will receive a "lead medal for their complicity in Sudan's campaign of violence," the coalition said in a statement.

Last month, the ruling Chinese Communist Party's flagship newspaper said China would never submit to political pressure from groups or governments wishing to use the Beijing Olympics to change Chinese policy.

The People's Daily said in a strongly worded opinion piece that people who believed they could pressure the Chinese government "have made the wrong calculation."