BAMAKO, Mali — An African force was formally transformed into a United Nations peacekeeping mission at a ceremony in Mali's capital on Monday, six months after French and African troops launched a military intervention to take back the country's north from al-Qaida-linked rebels.

The roughly 6,200 African troops, whose effectiveness in the field was hampered by major logistical lapses including units who were sent to Mali without weapons, will be folded into the Integrated United Nations Mission for the Stabilization of Mali, or MINUSMA. The force is expected to grow to more than 12,600 peacekeepers, though the timeline for the build-up is not clear.

"The composition of the MINUSMA is going to grow gradually in coming months," said Bert Koenders, a Dutch politician who is heading the mission.

In April, the U.N. Security Council authorized an 11,200-strong peacekeeping force and 1,440 international police to replace the 6,000-member African-led mission. The force is being led by military commander Maj. Gen. Jean Bosco Kazura, a Rwandan who was formerly head of the Rwandan Defense Forces Combat Training Center.

Before being integrated into the U.N. force, the African troops have long complained about the lack of supplies. A contingent in Burkina Faso based in the crucial northern city of Timbuktu, for example, said they could not fight the insurgents at night because they were missing night vision goggles. And the soldiers said they could not chase the extremists during the day because the rebels were using pickup trucks that ran on petrol, which drive faster than the gasoline-guzzling vehicles used by the military.

"This is a mission that has its own challenges, but we are here to say that we will find a solution to these obstacles," said Kazura. "Our goal is to accompany and support the peace process in Mali, and with everyone's help we will succeed."

Mali was plunged into near-anarchy last year when a junior military officer led a coup in the capital, toppling the nation's longtime leader. Insurgents in the north took advantage of the chaos to push into the main northern cities, succeeding in taking a France-sized territory. They ruled the area for 10 months until France launched a military intervention on Jan. 11.

The intervention was supposed to be a joint effort with African forces, but neighboring nations were slow to send troops and many came without crucial equipment and were left stranded in Bamako. The French swiftly moved north, and succeeded in liberating two of the three main towns in the north before the end of January.

With the exception of Chadian forces, who aggressively fought the insurgents in the Adrar des Ifoghas area of northern Mali, a foreboding landscape dubbed "Planet Mars" because of its red-colored and rocky terrain, the other African units largely played a support role. Many worry that with the drawdown of French forces, the insurgents will succeed in returning to Mali's deserted north and prove no match for the peacekeepers.