U.N. Secretary-General Kofi Annan told Sudan's government that he wants to see progress within 48 hours resolving a bitter conflict in the Darfur region, which his officials say has led to the world's worst humanitarian crisis.

As Annan joined Secretary of State Colin Powell on an unusually high-powered visit Wednesday, the United States called on the United Nations to impose an arms embargo and travel ban on Arab militias blamed for attacks on African villagers in Darfur (search).

The U.S. draft would put the U.N. Security Council on record expressing "its determination to do everything possible to avoid a humanitarian catastrophe, including by taking further action if required."

Annan has raised the possibility of sending in international troops if Sudan's government can't protect its people in the vast and desolate western region. Humanitarian workers have likened the attacks to ethnic cleansing.

"I think we all have a responsibility to act urgently to deal with the situation in Darfur," Annan told Sudanese Cabinet ministers Wednesday.

"We have worked together for a long time, and I hope this time we are going to take such measures that we don't have people in camps for years to come," Annan said. "I think we should be able to make some real progress in the next 24 to 48 hours."

Powell said he had given Sudanese leaders a timetable to implement its commitments to disarm the militias, known as the Janjaweed (search), as well as lift restrictions on relief workers and seek a resolution to the crisis. While he did not specify any deadlines, he said: "We are talking within days and weeks."

Powell briefed Annan about the steps the United States wants Sudan to take during a meeting upon his return from a trip to Darfur. Annan in turn informed Powell about his meeting with Cabinet ministers, U.N. associate spokesman Stephane Dujarric said at U.N. headquarters in New York.

The 16-month-old conflict has killed up to 30,000 people, driven more than 1 million people from their homes and left more than 2 million in desperate need of aid. Through their visit, the two leaders hoped to draw international attention to the crisis and ensure it is not ignored, like the Rwandan genocide was a decade ago.

Thousands of displaced Sudanese emerged from makeshift shelters at the Abu Shouk Camp on Wednesday to give Powell a raucous welcome. The camp is one of the temporary shelters in Darfur that house people uprooted over the last 16 months.

Powell, the first U.S. Secretary of State to visit the region in 26 years, avoided politically charged terms such as "ethnic cleansing" and "genocide" at a news briefing after the trip. He said the situation in Darfur was above all a security crisis.

"People are in camps because of the violence in their villages and countryside," he said. "We came to a common understanding that the Janjaweed must be controlled, they must be broken."

In an interview with National Public Radio, Powell said the situation "doesn't meet the tests of the definition of genocide."

"I can assure you that if all the indicators lined up and said this meets what the treaty test of genocide is, I would have no reluctance to call it that," Powell said.

Sudanese Foreign Minister Mustafa Osman Ismail (search), who accompanied Powell into Darfur, told reporters his government plans to send more police to secure the region and work swiftly toward a political settlement between the rival factions in the province.

"Hopefully in a very short time, we will reach agreement with the rebels," Ismail said.

Human rights groups have accused the Sudanese government of backing militias drawn from Arab herders in a campaign to forcibly remove African farming communities from the region, where they have coexisted for centuries.

Claiming that atrocities were being carried out with the "full cooperation" of the government, student protesters clashed with riot police Wednesday in the Sudanese capital.

The government had said it would tolerate no demonstrations during the visits by Annan and Powell. Witnesses said police fired tear gas and charged a few dozen protesters as they emerged from the campus of Khartoum University chanting anti-government slogans and hurling stones.

The government denies any complicity in the militia attacks and says the warring sides are clashing over land and scarce water resources.

The Justice and Equality Movement (search) and the Sudan Liberation Army (search), two groups drawn from the region's African tribes, took up arms in February 2003 over what they regard as unjust treatment by the government in their struggle over land and resources with Arab countrymen.