The Bush administration introduced a revised Security Council resolution on Thursday demanding that Sudan arrest and prosecute Arab militia leaders responsible for committing abuses in Darfur or face unspecified U.N. sanctions if it fails to comply within 30 days.

The move comes as U.S. Secretary of State Colin L. Powell charged the Sudanese government with "supporting and sustaining" the militia, known as the Janjaweed, which is believed to be responsible for killing tens of thousands of black African civilians in the region and driving more than 1 million from their homes.

Speaking to reporters after a meeting on Sudan with U.N. Secretary General Kofi Annan, Powell warned that Khartoum would face tough action if it failed to rein in the Janjaweed. He also pressed the government to end the ongoing aerial bombardment of villages in Darfur and to withdraw helicopter gunships from the region.

"Since they turned it on, they can turn it off," Powell said with Annan at his side. "And we're making it clear to them that there will be consequences if it is not turned off."

Sudan's foreign minister, Mustafa Osman Ismail, who has denied government support for the militia, criticized the United States for meddling in Sudan's internal affairs and said a new resolution would only "complicate" efforts to end the crisis.

Powell, meanwhile, said he has received initial reports from a team of U.S. officials in the region collecting evidence of war crimes and possible genocide in Darfur and that the United States "will make a judgment in due course as to whether it qualifies."

The U.S. strategy is calibrated to maintain the constant threat of sanctions against Khartoum, while relying on the government to take the lead in resolving the humanitarian crisis. Powell dismissed the possibility of U.S. military intervention in Sudan to stop the killing, saying "it is not a simple military solution that is at hand."

"Right now this is a matter for the Sudanese government to handle," he said.

The United States continues to face intense opposition to sanctions within the 15-nation council, particularly from China, Pakistan and Russia, which argue that Sudan should be given more time to meet its commitment to control the Janjaweed. But both Powell and Annan said they were confident that the council would ultimately adopt a final version of the resolution.

The three-page text demands Sudan "apprehend and bring to justice Janjaweed leaders and their associates who have incited and carried out" atrocities. It also "expresses" the council's "intention to consider further actions, including the imposition of sanctions on the government of Sudan, in the event of non-compliance."

The resolution also calls on Sudan to allow U.N. human rights monitors into Darfur, and appeals to wealthy governments to provide more funding to the humanitarian relief effort. Despite repeated requests for money, Annan said Wednesday that the United Nations has received only $145 million of the $349 million it needs to run its humanitarian operations in Sudan. The United States dropped a provision from a previous version of the resolution that put a travel ban on leaders of the Janjaweed militia, citing the challenges of enforcing the measure.

Instead, the new resolution calls for the imposition of an immediate ban on arms transfers and military assistance to armed groups in Darfur, including the Janjaweed and anti-government rebels.

Security Council diplomats said that it remains unclear how the measure would be enforced because the latest U.S. text dropped a provision from an earlier version that would have established a committee to monitor compliance.

The latest crises in Darfur began in February 2003 when rebels from the Sudan Liberation Army and the Justice and Equality Movement took up arms against the government, citing discrimination against the region's black tribes. U.S. officials and human rights groups charge that Khartoum recruited and equipped local Arab tribes to kill or drive out all potential civilian bases of support for the rebels.

Sudan promised Annan in a July 3 pact that it would provide access to international relief workers and crack down on the Janjaweed, but Powell and Annan have complained that the militia continued to mount attacks against civilians in Darfur, undermining efforts to distribute relief.

Foreign Minister Mustafa Osman Ismail criticized U.S. meddling in Sudan's affairs.