The new task force would work in much the same way to combat al-Qaida’s North African affiliates, which are growing in numbers and are awash in weapons from post-revolutionary Libya’s looted stockpiles. They are well-funded by a criminal network trafficking in drugs and hostages.

Al-Qaida in the Islamic Maghreb or AQIM, and Nigerian-based extremist sect Boko Haram are arguably the two largest and most dangerous affiliates. Both have morphed in recent years from extremist rebel groups that challenge their home governments into terrorist groups that use violence to try to impose extreme Islamic rule on any territory they can seize across Africa.

U.S. officials believe AQIM may have helped the local Libyan militant group Ansar al-Shariah carry out the Benghazi attack, and Boko Haram has killed more than 240 people in an anti-Christian, anti-government campaign of assassinations and bombings this year alone.

The governments of Libya and Niger have already asked for U.S. assistance to build their own special operations capability to help combat such al-Qaida-related groups, and Nigeria has requested help to control its porous border to stop militant trafficking, according to two U.S. officials. They, too, spoke only on condition of anonymity.

Mali has asked for international assistance to win back control of its northern region from al-Qaida groups including AQIM and Boko Haram, opening the possibility of a return of U.S. special operations forces there. A U.S. training unit was pulled out of the country after a March coup that gave the militants the chaos they needed to seize the northern territory.

The top State Department official for African affairs said Tuesday that the militants in Mali ‘‘must be dealt with through security and military means.’’

‘‘But any military action up there must indeed be well planned, well organized, well resourced and well thought through,’’ said Johnnie Carson, the U.S. assistant secretary of state for African affairs. ‘‘And it must, in fact, be agreed upon by those who are going to be most affected by it.’’

U.S. Africa Command chief Gen. Carter Ham said ‘‘a military component’’ would be a part of an overall solution in northern Mali, but he ruled out an overt U.S. military presence, speaking to reporters during a visit to Algeria over the weekend.

Asked about the attack in Benghazi, Ham said it’s the host country’s responsibility to protect diplomatic missions on its territory.

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Associated Press writers Pauline Jelinek in Washington, Aomar Ouali in Algiers and Krista Larson in Dakar contributed to this report.

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