(CNN) -- U.S. officials say that al Qaeda in the Arabian Peninsula, a fairly new arm of the umbrella terrorist organization, is behind an apparent plot to send explosive devices to U.S. destinations via cargo planes.
"Al Qaeda in the Arabian Peninsula is an organization of several hundred individuals that are dispersed throughout the country," presidential counterterrorism advisor John Brennan told reporters Friday. "They are murderers and they are determined to carry out attacks on innocent lives, whether they be Yemeni, Americans, Westerners or others. ...
"If anything, this just demonstrates to us and, I think to the Yemenis as well, that we need to redouble our efforts so that we're able to destroy al Qaeda, and we will."
Brennan pointed to the botched attempt last Christmas to blow up a Northwest Airlines passenger jet en route from Amsterdam, Netherlands, to Detroit, Michigan, on Christmas Day. U.S. and Yemeni officials have linked the attempt by man who tried to ignite explosives in his underwear to al Qaeda in the Arabian Peninsula.
Formed in 2009, al Qaeda in the Arabian Peninsula is a regional terrorist group known for targeting government and Western interests in Yemen and Saudi Arabia. Yemeni forces, with support from their U.S. allies, have stepped up military and political pressure on the group in recent weeks, despite continued threats from its leader.
A key figure in the group is Yemeni-American militant cleric Anwar al-Awlaki, whom U.S. authorities have linked to Fort Hood shooting suspect Maj. Nidal Hasan as well as the man accused in the Christmas Day bomb attempt. Brennan would not specifically name al-Awlaki as a suspect.
"Anybody who's associated with al Qaeda in the Arabian Peninsula is a subject of concern," he said.
"Clearly what we are doing is looking at all individuals that we think might be involved in this," Brennan said. "Al Qaeda in the Arabian Peninsula has been rather open in its venom towards the United States, towards Western interests. There are a number of individuals there that we're concerned about, so we're looking at all possibilities."
A senior U.S. defense official called al Qaeda in the Arabian Peninsula a "sophisticated" organization.
Combating the terror group has been a major focus for U.S. counterterrorism authorities, with Friday's incident underscoring the need for U.S. cooperation with Yemen, Obama said Friday.
"We ... know that al Qaeda in the Arabian Peninsula continues to plan attacks against our homeland, our citizens, and our friends and allies," said Obama. "Going forward, we will continue to strengthen our cooperation with the Yemeni government ... to destroy this al Qaeda affiliate."
Brennan said he talked Friday with Yemeni President Ali Abdullah Saleh about the threat posed by al Qaeda in the Arabian Peninsula and how to address it, receiving assurances from the Yemeni leader that they'd cooperate on the investigation.
These high-level talks are the latest in a series of collaborative efforts between U.S. and Yemeni officials and forces.
Earlier this year, the United States approved $150 million to train and equip Yemeni forces so they could fight al Qaeda in the Arabian Peninsula. Up to 50 U.S. special operations troops are now in the Middle Eastern country training Yemen's military personnel.
In addition, Yemeni and U.S. authorities have been sharing surveillance and other intelligence information culled from inside Yemen, a senior U.S. defense official said.
But Yemen announced Friday via its official news agency, Saba, that the army had ended its latest campaign against AQAP without finding any elements of the terror group.
"We found traces in the area of Khawaw indicating that al Qaeda elements were in this region three days ago," said Mahdi Abdul-Salam, a commander of the military campaign, adding that the extremist organization is no longer in the al-Kur mountain range in Yemen's southeast.
Many of al Qaeda in the Arabian Peninsula's members previously belonged to al Qaeda in Yemen. The National Counterterrorism Center says that group carried out suicide attacks on a Yemeni oil facility in 2006 and mortar attacks two years later on the U.S. Embassy in Yemen's capital, Sanaa, Yemeni military complexes, the Italian Embassy and the Yemeni presidential compound.
Later in 2008, al Qaeda in the Arabian Peninsula detonated two car bombs outside the U.S. Embassy in Sanaa, killing 19 people, including six of its own members, according to the National Counterterrorism Center.
Since forming under its new name, al Qaeda in the Arabian Peninsula has been tied to a pair of suicide bombings that targeted South Korean tourists.
On Monday, 15 suspected members of the group surrendered in Yemen's southern Abyan province, according to provincial Gov. Ahmed al-Maisari. The surrenders followed meetings with the governor and tribal sheikhs in the towns of Loudar and Moudeya.
Earlier in the month, Qassim al-Rimi (also known as Abu Hurira al-Sanaei), the military commander of al Qaeda in the Arabian Peninsula, posted an audio recording on radical militant websites.
The speaker promised that Yemen's president, Ali Abdullah Saleh, would be punished "for his crimes" and announced that a new army would rid the country of "crusaders and apostates." CNN could not verify the authenticity of the recording.