A new joint African Union-UN force took over peacekeeping in Darfur on Monday from an AU mission that failed to stem nearly five years of conflict in western Sudan.
A largely symbolic handover ceremony in Darfur's main city of Al-Fasher saw the AU troops of the now-defunct African Mission in Sudan force literally swap their green berets for the blue of the UN.
The mission, the UN's largest, will eventually consist of 20,000 troops and 6,000 police and civilian personnel, but only around 9,000 troops and police are currently in place.
The head of the new United Nations Mission in Darfur (UNAMID), Rodolphe Adada, appealed to the Khartoum government, which the US accuses of waging genocide in Darfur, and troop-contributing countries to do more.
"We are determined to deploy the most robust force possible so that it can carry out effectively the difficult mandate the Security Council has entrusted to it," Adada said as the UN flag was hoisted.
"This means contributing countries deploy their personnel as quickly as possible."
He appealed to rebels to negotiate, adding that the mission's bid to bring peace and stability to Darfur depended on "the active cooperation of the government of Sudan."
At least 200,000 people have died and more than two million have fled their homes since the ethnic minority rebels took up arms against Sudan's Arab-dominated regime in February 2003.
The government's response was to back the Arab Janjaweed militia and give it free rein to crack down on the rebels and their suspected civilian supporters.
Khartoum's representative at the ceremony, North Darfur governor Osman Yusuf Kibir, stressed his government's cooperation.
"We are fully committed to implement what has been agreed upon with the United Nations and the government of Sudan and the African Union ... we stress our full cooperation and commitment to the agreement," he said.
Washington called for an immediate and complete ceasefire, and US President George W. Bush signed a law on Monday aimed at piling economic pressure on Khartoum.
"My administration will continue its efforts to bring about significant improvements in the conditions in Sudan through sanctions against the government of Sudan and high-level diplomatic engagement and by supporting the deployment of peacekeepers in Darfur," he said in a statement.
Most of the new force comes from the 7,000 existing AU troops who have been trying to bring peace to Darfur for the past three years.
The underfunded and poorly equipped African force has faced an uphill struggle.
At least 50 African troops have died, 12 in a single attack on an AU base in September that was widely blamed on one of the increasingly fragmented rebel groups fighting government troops.
The bolstered force will have to face a security threat compounded by an escalating war of words between Sudan and neighbouring Chad as violence spilled over the border.
Sudan accused Chad on Friday of sending troops into its territory and said Chadian warplanes had bombed Darfur. Chad said it was "outraged" by the accusations.
UNAMID was authorized by the Security Council in July but it will not be fully operational until well into this year amid accusations Khartoum is stalling and that contributing countries are not supplying enough hardware, in particular helicopters.
The force, which has a budget of US$1.2 billion for this year, still needs 24 helicopters to patrol an area the size of France.