The United Nations will also provide material and logistic support to the mission, Blaise Compaore, president of Burkina Faso and head of the AU Peace and Security Council, said in New York on Wednesday.
Campaore also said he believed Sudan was ready to accept the mandate extension, decided on by 15 African leaders at the summit.
The AU’s mandate had been set to expire on September 30.
However Campaore also said that Sudan is still resisting demands that the United Nations take over the mission from the African Union.
Campaore said that under the new arrangement extra troops would also be sent to Darfur to support the mission.
He said that these would probably come from African countries, with further logistical support provided by the United Nations and additional inancial help given by the Arab League.
Three years of fighting
There are currently about 7,200 African Union troops in the western Sudanese region.
At least 200,000 people have died in the past three years in fighting and from disease and malnutrition caused by the conflict.
The summit also appealed for all sides in Darfur to respect the Abuja peace accords signed earlier this year.
The leaders agreed to support efforts to persuade Sudan to accept an eventual UN takeover of the international peacekeeping force.
In a speech to the UN General Assembly on Tuesday, George Bush, the US president, called the Darfur killings a genocide and said the AU force is “not strong enough” to protect the victims.
He called for the force to be strengthened and demanded the UN take control.