President George W Bush tightened US sanctions against Sudan on Tuesday and sought support for new international penalties out of frustration at Sudan's refusal to end the bloodshed in Darfur.
"The people of Darfur are crying out for help, and they deserve it," Bush said.
In brief remarks at the White House, Bush followed through on a threat made six weeks ago to pursue tougher action against a government he said was complicit in the bombing, murder and rape of innocent civilians.
"My administration has called these actions by their rightful name: genocide. The world has a responsibility to help put an end to it," he said.
Bush directed US Secretary of State Condoleezza Rice to consult with Britain and other allies on pursuing new UN Security Council sanctions against Sudan.
The aim of a new resolution, he said, would be to apply new sanctions against the Sudanese government and officials found to be violating human rights or obstructing the peace process, and to impose an expanded embargo on arm sales to the government of Sudan.
"It will prohibit the Sudanese government from conducting any offensive military flights over Darfur. It will strengthen our ability to monitor and report any violations," he added.
Bush, who has expressed frustration at the international community's inability to force Sudan to change its policy, urged Sudan's president, Omar Hassan al-Bashir, to let international peacekeepers into Darfur.
The ratcheting up of US pressure coincides with a broader effort by UN officials to get Sudan to end the conflict that the United Nations says has killed more than 200,000 people and driven 2 million from their homes since 2003. Khartoum says 9,000 have died and rejects accusations of genocide.
"I promise this to the people of Darfur: the United States will not avert our eyes from a crisis that challenges the conscience of the world," Bush said.
As part of the tightening of US sanctions, Bush said the US Treasury Department will bar 31 companies owned or controlled by Sudan from doing business in the US financial system, including a company that has been transporting weapons to the Sudanese government and militia forces in Darfur.
He also targeted sanctions against four Sudanese individuals, including two senior Sudanese officials and a rebel leader suspected of involvement in the Darfur violence.
Khartoum quickly criticized the sanctions before they were even announced, as did China, which is a major consumer of Sudanese oil.
"I think these sanctions are not justified. It is not timely. We are cooperating well with the United Nations," Mutrif Siddig, Sudanese undersecretary for foreign affairs, told Reuters in Khartoum.
In Beijing, China's representative on African affairs, Liu Guijin, said: "Expanding sanctions can only make the problem more difficult to resolve."
Asked whether UN Security Council member China would veto any new UN resolution targeting Sudan, he said: "It's still too early to speak of."
(Additional reporting by David Morgan in Washington and Cynthia Johnston in Khartoum)