Al-Qaida in the Islamic Maghreb has named a new chief for the vast Sahara and Sahel region as the jihadists brace for new offensives by the United States, seeking payback for the assassination of its ambassador in Libya, and African states.

Regional rivalries have stymied efforts by North African powers to move against the jihadists in a concerted manner but since AQIM and its allies conquered the northern region of Mali last spring, using veterans and weapons from Libya's civil war, there's been growing pressure for action.

The Americans, alarmed at the violent aftermath of that 2011 conflict, were galvanized when Ambassador Christopher Stevens was killed Sept. 11 in Benghazi, Libya.

Washington blames jihadists and pressure for decisive action against the spreading Islamist threat in North Africa is growing.

Regional security sources identified the new AQIM chieftain as Yahya Abou el Houman, who had led the group's Elvourghan brigade and had command of the ancient city of Timbuktu. He was appointed by AQIM's overall leader, the veteran Abdelmalek Droukdel, aka Abu Musab Abdel-Wadoud, the sources said.

Houman succeeds Nabil Makhloufi, who was reportedly killed in a car crash Sept. 10 driving at high speed between the Islamist held cities of Gao and Timbuktu.

"The al-Qaida node has suffered several operational and leadership disruptions in recent months and AQIM brigades and Malian authorities have both been behaving in ways that portend an escalation in counterterrorism operations," the U.S. global security consultancy Stratfor observed.

Algerian newspapers report AQIM forces are strengthening defenses of their strongholds in northern Mali with minefields and trench systems. The Islamists seized this territory from former Tuareg tribal allies who overran the region in March in the aftermath Moammar Gadhafi's downfall in Libya to declare a secessionist state.

The establishment of a jihadist enclave in the remote Sahel region has alarmed regional powers led by Algeria, which fought a decade-long war against Islamist rebels throughout the 1990s, Mauritania and others.

AQIM was formerly the diehard Salafist Group for Preaching and Combat, which broke away from the Armed Islamic Group, the most bloodthirsty of the Islamist groups that fought the Algerian government.

The group has become the strongest Islamist organization in North Africa and is closely allied with Mali's two jihadist outfits, Ansar Dine -- Defenders of the Faith -- and the Movement for Unity and Jihad in West Africa, known as MUJAO.

Much of AQIM's funds -- an estimated $50 million in recent years -- come from kidnappings for ransom, particularly involving Westerners.

With the Islamist militants firmly dug in across Mali and exploiting political upheaval in the Arab world, the jihadist threat in North Africa has grown alarmingly.

The United States is slowly becoming involved in the counter-terrorism effort, primarily through the Africa Command established in 2007 to train regional counter-terrorism forces.

U.S. units reportedly operate unmanned aerial surveillance vehicles out of a desert base in Morocco, with a similar Special Operations base in Burkina Faso.

Since Stevens was killed, some say as retaliation for a purported U.S. plot to kill AQIM's Droukdel, U.S. Special Forces have been quietly deployed at U.S embassies across the region, although no unilateral action is reportedly contemplated.

French Special Forces have been involved in covert actions against AQIM with regional forces. France, the former colonial power in much of the region, openly favors military intervention against AQIM.

French Foreign Minister Laurent Fabius said during a recent visit to Algeria, which Paris wants to spearhead a regional offensive, that AQIM is "the main enemy."

The use of force was probable "sooner or later," he said.

Algeria is the main military power in the Sahel and in recent years has sought to lead regional moves against the jihadists, in large part to ensure that France and other Western power keep out of the region.

Algeria, which waged a 1954-62 independence war against France, fears that "military intervention could awaken regional, religious or ethnic extremism and risks opening a Pandora's box," observed Rachid Tlemcani, professor of international politics and regional security at the University of Algiers.

"An explosion in the south would destabilize the north all the way to Morocco," he warned.