The decision was made during the African Union meeting this weekend in Gambia.
Republic of Congo leader Denis Sassou Nguesso, who currently holds the rotating AU presidency, said decision was made at the request of the UN Secretary General.
The AU had planned to withdraw its force from Darfur by the end of September because of the cost.
But UN chief Kofi Annan had asked the African leaders at the summit for "flexibility" on their original plan, promising he would raise funding for the force at a donors conference on July 18.
Sudanese leader Omar al-Beshir has been strongly against the UN deployment but Mr Annan said ongoing discussions with Khartoum on the international troop intervention could yield positive results.
"In the world of politics things change, we hear 'never', 'forever' and yet it does come around and I still suspect in time there will be UN peacekeeping force in Darfur," said Mr Annan.
The UN chief said the planning for deployment "is very well advanced... we do hope still to deploy the troops."
He said Mr Beshir had promised to submit to him before end of July his "plan for the next six months" on easing the crisis in Darfur.
In Darfur, which is roughly the size of France, up to 300,000 people have been killed and 2.4 million displaced by three years of civil war.
Other issues discussed
On Somalia, Sassou Nguesso said the summit "agreed to give its full support to the transitional government ...while favouring dialogue inside Somalia."
On migration from Africa to Europe, Mr Nguesso said Africa did not believe that the "few measures" adopted by European countries would help solve the illegal migration crisis.
"It will not help to set up barbed wire or to decide on a few administrative matters, these are not solutions," said the AU chief.
"As long as there is poverty...injustice persists, it will not be possible to bring this dramatic situation to a close," he said.
Thousands of African migrants have in recent months died at sea while on perilous journeys to Spain in barely seaworthy dug-out canoes.