"The death of Awlaki is a major blow to al-Qaeda's most active operational affiliate. Awlaki was the leader of external operations for al-Qaeda in the Arabian Peninsula. In that role, he took the lead in planning and directing efforts to murder innocent Americans," Obama said.
He made the remarks on Friday at an event held to bid farewell to Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, hours after Awlaki, a Yemeni-origin American engineer, was killed in a US drone attack in Yemen.
"The death of Awlaki marks another significant milestone in the broader effort to defeat al-Qaeda and its affiliates. Furthermore, the success is a tribute to our intelligence community and to the efforts of Yemen and its security forces, who have worked closely with the United States over the course of several years," the President underlined.
Obama said Awlaki had directed the failed attempt to blow up an airplane on Christmas Day in 2009. He had also directed the failed attempt to blow up US cargo planes in 2010.
"And he repeatedly called on individuals in the United States and around the globe to kill innocent men, women and children to advance a murderous agenda," the President said.
In his reaction, US Defence Secretary Leon Panetta said the US is much safer now.
"This has been a bad year for terrorists. We just have seen a another major blow to al-Qaeda, someone who was truly an operational arm of al-Qaeda in this node of Yemen," Panetta told reporters here.
"We had always had tremendous concern that after getting (Osama) bin Laden, that someone like Awlaki was a primary target because of his continuing efforts to plan attacks against the United States," Panetta said.
"He continued to try to inspire people to terrorise this country and to attack this country. And so this country is much safer as a result of the loss of Awlaki," he said.
Refusing to go into operational details, Panetta said the United States has been working with Yemenis over a long period of time to be able to target Awlaki.
"I want to congratulate them on their efforts, their intelligence assistance, their operational assistance to get this job done," he said.
Responding to questions, Panetta said there is no question that in the last few years the intelligence community and the military community have really come together as partners in going after terrorism.
"The President of the United States has made very clear that our primary mission is to disrupt, dismantle and defeat al-Qaeda.
And that has been the target of all of these efforts," he noted.
"What happened to bin Laden, what's happened to the top leadership in al-Qaeda and what happened with Awlaki is the result of a lot of efforts coming together," he said.
In this instance, the Yemenis themselves have long cooperated with the United States in this effort, Panetta said.
"It goes back, frankly, to before some of the turmoil we've seen there, that the relationship in sharing intelligence and going after this target was something that involved a tremendous amount of cooperation between the United States and the Yemenis, and today it paid off."