French forces have encountered little resistance as they help the Malian military take on foreign and al-Qaida fighters. Mali issued a Jan. 11 request to France, the former colonial power, to help thwart the rebel advance south.
Costello told U.N. and African Union officials in Brussels that a coordinated effort was needed to ensure stability in Mali.
"Good progress has been made in stabilizing the security situation in Mali in recent weeks, but now it is vitally important that the provision of humanitarian aid and the political process keep pace," he said.
The government lost control over northern Mali in an early 2012 coup.
The United Nations and chief prosecutor at the International Criminal Court have expressed concern that Malian forces may seek revenge as they push north. Rebels are also accused of crimes, including the destruction of heritage sights in the historic city of Timbuktu.
Regional leaders told the U.N.'s humanitarian news agency IRIN that calm was returning to the city, however.