U.S. President George W. Bush and other leaders should shun the Beijing Olympics opening ceremony unless China does more to stop bloodshed in Sudan's Darfur region, activists said on Thursday.

The umbrella group of Darfur organizations said it was not advocating that countries, athletes or corporate sponsors boycott the August 8-24 Games. But it said host China's close ties to Sudan undercut the spirit of the opening ceremony.

"Beijing should not be allowed to bask in the warm glow of peace and brotherhood associated with the opening games if China is still underwriting atrocities in Darfur and still has not done what it should to bring peace and security to Sudan," said the group in a statement from Washington.

"We call on world leaders not to attend the opening ceremony of the 2008 Beijing Olympics," it said.

The group - from Save Darfur Coalition, ENOUGH Project, STAND: A Student Anti-Genocide Coalition, Genocide Intervention Network and Dream for Darfur - vowed to continue their call for a ceremony boycott until Sudan accepts deployment of a hybrid U.N.-African Union peacekeeping force in Darfur.

Only 9,000 of the planned 26,000 international troops and police have been deployed in Darfur. Western governments have blamed Khartoum for dragging its feet in approving the composition of the force and creating other obstacles.

China's diplomatic and economic support for Sudan enabled Khartoum to stonewall on the peacekeepers, the activists said.

"As Sudan's largest economic partner, major military supplier, and chief diplomatic supporter, Beijing is in an unrivalled position to persuade Sudan to change its behaviour," said the statement.

China, under fire from rights groups for its policies in Tibet and for jailing critics ahead of the Olympics, has rejected efforts to link its Darfur policy to the games and bristled at talk of a boycott.

Bush has resisted calls to rethink his plans to attend the Beijing Games, saying he will raise rights and other concerns in private with his host, Chinese President Hu Jintao.

French President Nicolas Sarkozy has floated the idea of boycotting the opening ceremony in response to China's suppression of Tibetan protests last month.

About 2.5 million people have fled their homes during the five-year war in Sudan's west. International experts estimate some 200,000 have died in violence Washington calls genocide.

Khartoum denies genocide and puts the death toll at 9,000.