WASHINGTON (CNN) -- President Obama's top counterterrorism adviser Thursday vowed the U.S. would defeat al Qaeda and declared the president has urged him to be more aggressive in destroying the terrorist organization.
White House adviser John Brennan says al Qaeda is seriously damaged but resilient.
John Brennan, Obama's senior adviser on counterterrorism and homeland security, projected an assertive stance toward the battle against al Qaeda -- which Brennan said "remains the most serious threat" the U.S. faces -- and al Qaeda's allies in Afghanistan and Pakistan.
He made clear that predator drone attacks would continue, while minimizing collateral damage that enemies can exploit for propaganda.
"President Obama is under no illusions about the imminence and severity of this threat," Brennan told a gathering at a Washington think tank.
"Not only has he approved these operations, he has encouraged us to be even more aggressive, even more proactive, and even more innovative to seek out new ways and new opportunities for taking down these terrorists before they can kill more innocent men, women, and children," Brennan said.
Brennan said al Qaeda "has been seriously damaged and forced to replace many of its top-tier leadership with less experienced and less capable individuals."
"Nevertheless," he said, "al Qaeda has proven to be adaptive and highly resilient and remains the most serious terrorist threat we face as a nation."
Brennan said the aggressive immediate campaign to destroy al Qaeda must be coupled with a longer-term plan to confront violent extremism generally. He said that includes economic help to restore legitimate institutions.
"In Afghanistan this means a dramatic increase in our development efforts. ... In Pakistan it means $1.5 billion in direct support every year for education, health care and infrastructure," Brennan said.
Brennan said closing the prison camp at the U.S. naval base at Guantanamo Bay, Cuba, will help in combating terror recruitment.
He stopped short of an iron-clad promise that the prison would be entirely empty by January.
"It is our full intention to close it down to meet the deadline," Brennan said. However, he added that it is unknowable whether detainees will still be there in January.