Thousands of Sudanese refugees have rushed to welcome US Secretary of State Colin Powell in a camp in the troubled western province of Darfur.
About one million people in Darfur have been driven from their homes
They shouted and cheered, following his motorcade round the Abu Shouk camp, says the BBC's Jill McGivering.
Mr Powell earlier warned the Sudan government to rein in Arab militias accused of ethnic cleansing in Darfur.
The UN Security Council could act in the region where about one million people have fled their homes, he said.
UN Secretary General Kofi Annan has also gone to Sudan to discuss Darfur.
Mr Powell - the highest-ranking US official to travel to Sudan in two decades - has said the crisis may yet turn out to be genocide.
In response, Sudan's Foreign Minister Mustafa Ismail promised to send more forces to protect civilians and ease restrictions on humanitarian workers.
The BBC's Ishbel Matheson in Khartoum says the government has made similar pledges before.
The US and the UN, she says, are now insisting that they should be turned into reality.
Mr Powell's Jeep was instantly mobbed as it entered the camp.
One of those who followed him told AFP news agency that he feared there were spies there, and repeatedly made a throat-cutting gesture as he said "Janjaweed" - as the dreaded Arab militias are known.
The Abu Shouk camp is one of the best and is accessible to humanitarian agencies.
Some 40,000 people live under plastic sheeting and makeshift tents - although malnutrition is rife.
At a joint news conference after Mr Powell's arrival in Sudan on Tuesday, he accepted there was a "problem" in Darfur, but suggested it had been exaggerated.
"We believe that there is no famine, no epidemic, but that does not mean that there is no humanitarian problem which needs to be taken care of," he said.
Mr Powell held talks with Sudanese President Omar al-Bashir on Tuesday equipped with satellite photographs of empty, ruined villages in Darfur.
He said afterwards he had made three main demands:
- Sudan must rein in the Arab militias which observers say have been sponsored by the government in Darfur
Humanitarian agencies must be given full access to the region
The government must start negotiations with Darfur's two rebel movements
"Unless we see more moves soon in all these areas, it may be necessary for the international community to begin considering other actions, to include Security Council action," Mr Powell said.
Earlier, he said the death rate seemed set to "go up significantly" in Darfur.
Between 300,000 and one million people could starve in the region, says the head of the US Agency for International Aid, Andrew Nations.
"We see indicators and elements that would start to move you toward a genocide conclusion but we're not there yet," Mr Powell said en route to Khartoum from Turkey.
"We can find the right label for it later, we have got to deal with it now."
Mr Annan has refused to use the term genocide, which would entail a legal obligation for the international community to take action.
Mr Annan has also warned the UN Security Council may act if Sudan fails to tackle the crisis which developed after two rebel groups took up arms against the government in February of last year, demanding more rights for black Africans.
If Sudan does not protect people in Darfur, "the international community has to do something about it," he said during a visit to Qatar on Tuesday.
The UN has described Darfur as "the worst humanitarian crisis in the world".
An estimated 10,000 people have been killed and a ceasefire signed more than two and half months ago is violated on an almost daily basis by the warring sides.
The government denies supporting the Janjaweed, accused of leading the attacks on black Africans, and President Bashir has ordered the militia to be disarmed and prosecuted.
However, the BBC's Alfred Taban reports from Khartoum that aid agencies and black civilians believe the army is unwilling to deal with the Janjaweed because they have been effective in checking the rebels in Darfur.