The humanitarian disaster unfolding in Darfur was due to receive its most prominent exposure so far on American television last night. But it says much about the interface between politics and celebrity that the coverage was not to be found on any of the three main evening news broadcasts, which have devoted only 10 minutes to the crisis between them since the start of the year. Instead, it was an episode of the hospital drama ER - with the show's heart-throb doctor John Carter (played by Noah Wyle) in the thick of a tragedy the news media have been condemned for neglecting.

The episode, which cost $7m (�3.8m), has coincided with several TV talkshow appearances by George Clooney, a former star of the series, to mark a high point for the visibility of Darfur, where at least 180,000 people have been killed and millions more displaced in the past three years. Clooney, who recently travelled to the region, also addressed a rally in Washington on Sunday, one of several across the US.

As the fiction reached American screens last night, events in reality were progressing fast, with rebels indicating that they would accept a US and British-brokered peace proposal that would see thousands of rebels integrated into Sudanese security forces.

Viciousness

"The conditions under which people operate are much worse [than portrayed on ER]," said Eric Reeves, a leading Sudan scholar who watched an advance screening of the episode. But he said the producers had been able to capture "some sense of the viciousness" of the government-backed Janjaweed militias. "It was prime-time television, and you can't do Darfur [on prime-time television]. But you can give a suggestion. It gave a good-faith suggestion."

Clooney and fellow celebrities Angelina Jolie and Hotel Rwanda star Don Cheadle are the most high-profile figures in a movement that has been gaining ground for many months, forging an unlikely alliance between leftwing students and rightwing Christians, and spanning both sides of an otherwise bitterly divided Congress. And while humanitarian groups say the Bush administration's response only begins to address the scale of the disaster, it is evident that the campaign has succeeded in influencing the White House.

As part of a grassroots campaign that far outstrips anything Europe has seen, Harvard, Stanford, Yale and several other universities have divested funds from companies deemed complicit in supporting the Sudanese government.

"This has to do a lot with students who aren't really old enough to remember Rwanda, but nonetheless are aware that they risk having on their watch a Rwanda in slow motion," said Professor Reeves, who teaches at Smith College in Massachusetts. "Americans have understood from the beginning, in ways that for whatever reasons are not apparent to Europeans, that this is genocide."

Former secretary of state Colin Powell took a decisive step in 2004 when he used the word "genocide" to describe the slaughter in Darfur, and George Bush now uses it frequently. In the same year, the European parliament stopped short of endorsing the use of the term, calling the crisis "tantamount to genocide".

Meanwhile, the Christian right, a crucial constituency for Mr Bush, has seized upon the issue - continuing a history of opposition to the Islamic government in Khartoum for its persecution of Christians in the south, even though most of the Janjaweed's victims in the current conflict have been Muslim.

"The long-term trend is that conservative Christians have become interested in foreign policy questions, including sex trafficking, Aids and third-world debt," said John Green, of the Pew Forum on Religion and Public Life. "They're adopting approaches to evangelising that Roman Catholics, and other protestants, adopted a generation earlier - the notion that in order to effectively bring people to Christ one has to address their economic and social needs as well as their spiritual needs."

Expedient

Sceptics say the issue is a politically expedient one for Mr Bush, permitting diffuse and generalised statements of compassion, along with backing for enhanced multinational action, without touching on any of the divisive themes underlying debate on Iraq and Iran.

"It's incredibly easy to say, 'This is unacceptable'," said Ian Levine at Human Rights Watch in New York. "But, to [Mr Bush's] credit, he did not veto the security council referring the matter to the international criminal court, despite the administration's opposition to the court. There was a struggle for the soul of the White House, it seems, and in that case, the Darfur lobby won."

The issue is also politically awkward for the White House because the CIA has been trying to forge relations with Khartoum as a source of intelligence on terrorism. Osama bin Laden based his embryonic network in the Sudanese capital before moving to Afghanistan.