KHARTOUM, Sudan, June 30, 2004 (AP) -- U.N. Secretary-General Kofi Annan told Sudanese government representatives Wednesday that he wants to see progress within the next 48 hours in resolving a bitter conflict in the Darfur region, which his officials call the world's worst humanitarian crisis.

As Annan joined U.S. Secretary of State Colin Powell on an unusually high-powered visit, the U.S. called on the U.N. to impose an arms embargo and travel ban on Arab militias blamed for waves of attacks on African villagers in Darfur, which humanitarian workers liken to ethnic cleansing.

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 safeguard its people in the vast and desolate western region.

"I think we all have a responsibility to act urgently to deal with the situation in Darfur," Annan told Sudanese Cabinet ministers at the start of a meeting that also included senior officials from the U.N.

"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, particularly the Janjaweed, lift restrictions on relief workers and seek a resolution to the crisis. While he didn't specify any deadlines, he said: "We are talking within days and weeks."

Powell briefed Annan about the steps the U.S. 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, two leaders hoped to draw international attention to the crisis and ensure it is not ignored as the Rwandan genocide was a decade ago.

Thousands of displaced Sudanese emerged from makeshift shelters Wednesday to give a raucous welcome to Powell at the Abu Shouk Camp, one of the temporary shelters around beleaguered Darfur province 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."

Sudanese Foreign Minister Mustafa Osman Ismail, who accompanied Powell into Darfur, told reporters that his government plans to send in 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 and in some cases intermarried 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 declared it would tolerate no demonstrations during the visits by Annan and Powell, and witnesses said baton-wielding 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.

Five students were injured by rubber bullets and nine others were being treated after inhaling tear gas, an organizer of the protest said. Other students were caring for the injured at a youth hostel, which police had surrounded, the organizer said, speaking on condition of anonymity.

Earlier in the day, police blocked students who tried to deliver an open letter addressed to Annan to U.N. offices in the city.

The three-page letter, a copy of which was obtained by The Associated Press, urged the U.N. to "bring those responsible for the atrocities to the court of law."

U.N. officials said they were trying to arrange for the petition to be delivered to Annan.

Annan said last week that the situation is "bordering on ethnic cleansing," and U.N. human rights investigator Asma Jahangir said Tuesday she saw "strong indications of crimes against humanity" during a 13-day visit to Darfur in early June.

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 and the Sudan Liberation Army, 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.

The rebel movements also are confronting Arab militias blamed by humanitarian groups for attacks that have razed hundreds of villages.

Friday, Annan visits Sudanese refugee camps in neighboring Chad before returning to Khartoum for a meeting with Sudanese President Omar el- Bashir.