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Secretary of State Colin Powell said Thursday the Sudanese government has yet to follow through on promises to help those in the Darfur region who are "imperiled by violence, starvation and disease."

"We need immediate improvement," Powell said, warning that a Sudanese failure to act could lead to tough U.N. Security Council sanctions against the country's Islamic government.

"Despite the promises that have been made, we have yet to see dramatic improvements," Powell told a Capitol Hill seminar on Africa policy convened by the Center for Strategic and International Studies.

Arab militias known as the Janjaweed have carried out a ruthless counterinsurgency campaign against a rebellion by black African groups which accuse the Sudanese government of grossly neglecting their interests.

In the process, the militias have carried out rape and pillage and razed hundreds of villages, causing a huge humanitarian crisis.

"Only actions, not words, can win the race against death in Darfur (search)," Powell said.

Powell made Wednesday by the new U.S. ambassador to the United Nations. John Danforth (search), who said Sudan (search) has but days to act before facing the prospect of U.N. sanctions.

A U.S. draft resolution calls on Sudan to immediately fulfill all its commitments to end violence in the western Sudanese region and to give access to aid workers. The resolution also urges the warring parties in Sudan to conclude a political agreement without delay and it commits all states to target sanctions against the government-backed militias held responsible for the crisis.

"The government of Sudan bears the greatest responsibility to face up to this catastrophe, rein in those who are committing this ethnic cleansing and save the lives of its own citizens," Powell said.

Last week, Powell made a brief visit to a refugee camp in Darfur after discussions with President Omar el-Bashir in Khartoum. By week's end, el-Bashir had pledged to send troops Darfur to end militia violence and to remove all obstacles to delivery of relief supplies. There also were promises to start a peace dialogue among the rival factions.

"We will not rest. We will continue to apply pressure," Powell said, adding that swift action is needed because the onset of the rainy season means delivery of relief supplies will be more difficult.

Powell said some of the displaced in Darfur "have already been consigned to death" because of dire conditions. "They will not make it through the end of the year, through the fall," he said.