If Barack Obama wants to help end the genocide in Darfur, he doesn’t have to look far for ideas of how to accomplish that. President Bush and his top aides have been given, and ignored, a menu of options for tough steps to squeeze Sudan — even destroy its air force — and those will soon be on the new president’s desk.

The State Department’s policy planning staff prepared the first set of possible responses back in 2004 (never pursued), and this year Ambassador Richard Williamson has privately pushed the White House to squeeze Sudan until it stops the killing.

Mr. Williamson, who is President Bush’s special envoy to Sudan, wrote a tough memo to Mr. Bush this fall outlining three particular steps the United States could take to press Sudan’s leader, President Omar Hassan al-Bashir:

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The United States could jam all communications in Khartoum, the Sudanese capital. This would include all telephone calls, all cellular service, all Internet access. After two days, having demonstrated Sudan’s vulnerability, the United States could halt the jamming.

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The United States could apply progressive pressure to Port Sudan, from which Sudan exports oil and thus earns revenue. The first step would be to send naval vessels near the port. The next step would be to search or turn back some ships, and the final step would be to impose a quarantine and halt Sudan’s oil exports.

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The United States could target Sudanese military aircraft that defy a United Nations ban on offensive military flights in Darfur. The first step would be to destroy a helicopter gunship on the ground at night. A tougher approach would be to warn Sudan that unless it complies with international demands (by handing over suspects indicted by the International Criminal Court, for example), it will lose its air force — and then if it does not comply, to destroy all its military aircraft on the ground.

Officials frustrated by the administration’s passivity shared these possible steps with me, partly to make clear that Mr. Obama can do more if he has the political will.

Mr. Williamson has been one of the unsung heroes of the Bush administration, fighting tenaciously and secretly — even twice threatening to resign — to redeem American honor by confronting genocide. President Bush himself seemed open to tougher action, officials say, but Secretary of State Condoleezza Rice and Stephen Hadley, the national security adviser, always resisted, backed by the Pentagon. Ms. Rice and Mr. Hadley tarnished their own honor and America’s by advocating, in effect, acquiescence in genocide.

The naysayers’ objection was simple: Those are incredibly serious steps, with grave repercussions.

They’re right. But then again, genocide is pretty serious, too.

That’s something that Mr. Obama and his aides understand. Partly for that reason, Sudan fears the Obama administration, and now for the first time in years, there’s a real chance of ousting President Bashir and ending his murderous regime.

Several factors are coming together. The leaders in Khartoum feel their government wobbling, particularly after rebels clashed with government soldiers on the outskirts of Khartoum earlier this year. They know that the International Criminal Court is expected to issue an arrest warrant for President Bashir, probably in February, but that no other top leader will be indicted after Mr. Bashir.

China, which for years has been President Bashir’s most important international supporter, now seems to be backing away — just as it eventually abandoned genocidal friends like Slobodan Milosevic and the Khmer Rouge. And an Arab state, Qatar, is now leading a serious diplomatic initiative to try to end the slaughter.

Thus there are growing whispers that key figures in the Sudanese regime may throw Mr. Bashir overboard in the coming months. The other leaders are ruthless and have blood on their hands as well, but some of them have in the past proved more willing to negotiate deals than Mr. Bashir has.

Hovering in the background is the risk that the north-south war in Sudan will resume, leading to a slaughter even worse than Darfur. One ominous sign is that Sudan is now stockpiling cash and weapons, apparently so that it can wage war on the south even if Port Sudan is blocked.

Mr. Williamson has suggested providing surface-to-air missiles to the separate government of South Sudan. Such weaponry would reduce the chance that Sudan would attack the south.

If Mr. Obama and his aides can work with Europe, China and Qatar to keep the heat on — and to make clear that Sudan has no choice but to hand over President Bashir once the court issues the arrest warrant — then we just might avert a new war and end the first genocide of the 21st century in the new year.