UN Secretary General Kofi Annan has told the opening of the African Union summit that a "catastrophe" was looming in Sudan's Darfur province.
Many thousands are starving in Darfur, aid workers say
He warned the crisis may destabilise the entire region and said Sudan had a "sacred duty" to help its citizens.
Some one million people have fled their homes in 16 months of conflict.
Sudan has approved new security plans for the refugees and the African Union has agreed to send soldiers to protect its ceasefire monitors in Darfur.
The interior minister in Khartoum said it would install police stations in the refugee camps to "receive complaints about human rights abuses and adopt all measures... to restore justice."
Pro-government Arab militias have been accused of "ethnic cleansing" against Darfur's black African population.
"Without action, the brutalities already inflicted on the civilian population of Darfur could be a prelude to even greater humanitarian catastrophe, a catastrophe that could destabilise the region," Mr Annan said.
He also urged Darfur's rebel groups "to respect the ceasefire and work with the government to end the conflict peacefully".
Following intense international pressure, the Sudanese government has lifted a number of restrictions on the imports of aid supplies and the movement of relief organisations in Darfur.
Some 300 AU troops will be deployed to guard the 40 monitors who have so far been unable to start work due to a lack of security.
AU Peace and Security Director Sam Ibok said Nigeria and Rwanda were ready to contribute and they were talking to Tanzania and Botswana as well.
He appeared confident the Sudanese government would accept the armed force, although there has been no word from Khartoum.
The government is accused of arming militia groups in Darfur to defeat the rebels but the militias have attacked villages, killed thousands and displaced more than a million.
Sudan has pledged to disarm the Arab militia, known as the Janjaweed, who have terrorised villages and left thousands dead.
The AU appears to be taking a twin-track approach to the crisis, boosting the effectiveness of their observers, while increasing diplomatic efforts to find a solution.
Fresh talks between the Sudanese government and rebel groups are planned for next week in Addis Ababa.
The AU, which was set up to replace the ineffective Organisation of African Unity, is now apparently making a major effort to be more assertive in how it deals with its members.
West African leaders at the summit have also announced plans for fresh peace talks in late July aimed at ending the stand-off in the Ivory Coast.
Other items on the agenda for some 40 African leaders include:
- A proposal that all members should pay 10% of the defence budgets to the AU to set up a pan-African defence force by 2010.
- Hopes for similar regional talks on Democratic Republic of Congo were hit when Congolese President Joseph Kabila announced that he would no longer be travelling to Ethiopia.
- UN Secretary General Kofi Annan has urged member states to boost food production by pursuing a "green revolution" which would include better irrigation, improved food crops and better infrastructure.
- They may discuss a human rights report on Zimbabwe, which has been gathering dust since 2002 but which was adopted by the AU executive council on Monday, despite intensive lobbying by Zimbabwe.
- An economic advisor to Mr Annan has also raised the issue of refusing to pay debts if they were not cancelled.