The U.S. airlift of French forces to Mali to fight Islamic extremists is expected to go on for another two weeks, Pentagon officials said, as hundreds of African troops from Nigeria, Togo, Burkina Faso and Senegal are now joining the French-led intervention.

The Islamist fighters have controlled the vast desert stretches of northern Mali, with the weak government clinging to the south, since a military coup in the capital in March last year unleashed chaos.

The U.S. Air Force is keeping between eight and 10 people at the airport in Mali's capital to help with the incoming and outgoing flights, the Pentagon said late Tuesday.

The U.S. Air Force already has flown five C-17 flights into Bamako, delivering more than 80 French troops and 124 tons of equipment, it said.

U.S. State Department spokeswoman Victoria Nuland said between 700 and 800 African forces were arriving Tuesday in Mali.

"We've been pushing all of the ECOWAS countries for more than a month now to look at what they could do in terms of available forces in terms of the kinds of capabilities that were required," Nuland told reporters in Washington.

She said Chad has also committed between 1,000 and 2,000 soldiers depending on the need, and they are on their way to Mali.

"Chad is a country that does have a relatively robust and well trained set of forces," she said. "They also have interests to protect in the neighborhood, and we have been working with them to get them ready."

Nuland on Tuesday praised the Malian forces for retaking the key towns of Diabaly and Douentza with the help of the French.

The town of Douentza had been held by Islamist rebels for four months and is located 195 kilometers (120 miles) northeast of Mopti, the previous line-of-control held by the Malian military in Mali's narrow central belt. French and Malian troops arrived in Douentza on Monday to find that the Islamists had retreated from it.

French and Malian forces also took the town of Diabaly, which lies 195 kilometers (120 miles) west of Mopti, on Monday after Islamist fighters who had seized it a week earlier fled amid French air strikes.

"They are making some progress," Nuland said. "It'll be important to be able to hold that territory, continue to make progress going forward," she said.

The U.S. is not providing direct aid to the Malian military because the democratically elected government was overthrown last March in a coup.

The French-led operation to oust Islamic extremists from northern Mali began Jan. 11. France has said it will stay as long as necessary but that other African countries must take the lead in helping Mali.