Adviser: Obama urging 'more aggressive' fight against al Qaeda

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.

Brennan said the president's strategy starts with pushing the Taliban out of key population areas in Afghanistan.

"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.