French forces rolled back Islamist militants in Mali "much faster" than the United States expected but now face the daunting task of building long-term security in the region, US Defense Secretary Leon Panetta said Friday.
"They have made tremendous progress, I give them a lot of credit," Panetta told AFP in an interview at the Pentagon.
"They have moved much faster than we had anticipated. They now control Timbuktu and Gao and have moved into the north to capture some of the cities in the far north as well.
"That's very good progress," Panetta said.
Despite the swift advance, the most difficult challenge lies ahead to ensure security does not unravel again, said Panetta, who is due to retire from his Pentagon post later this month after decades in Washington.
"But the challenge now is to make sure that you can maintain that security and that you are not overstretched and that, ultimately, as you begin to pull back, that the other African nations are prepared to move in and fill the gap of providing security.
"And that's going to take some work," he said.
French President Francois Hollande was to visit Mali on Saturday and appeal to African nations to take the lead from France in the fight against Islamist militants.
France is keen to hand over its military operation to nearly 8,000 African troops slowly being deployed, which the United Nations is considering turning into a formal UN peacekeeping operation.
The French campaign, launched three weeks ago after a push south by rebel fighters raised fears the country could become a sanctuary for Al-Qaeda-linked extremists, has claimed a rapid succession of victories in key Islamist strongholds.
Panetta spoke as French troops were poised to secure the northeastern outpost of Kidal, the rebels' last bastion.
He said the US military would look to bolster its efforts in the region to counter Al-Qaeda affiliates and assist African armies against the militants.
"The United States has to take whatever steps are necessary to make sure that Al-Qaeda has no place to hide," said Panetta, who served as CIA director before taking over the Pentagon in 2011.
"It was always clear to me that AQIM (Al-Qaeda in the Islamic Maghreb) was an element of Al-Qaeda that we had to keep our eye on, and that has proven true," said Panetta, referring to the terror network's branch in Africa's Sahel region.
Asked about plans to use an air base in Niger under a new agreement, Panetta said the US military's Africa Command would do everything possible "to try to work with the countries in that region to make sure that AQIM is not only weakened but ultimately defeated there as well."