WASHINGTON -- The U.S. will keep targeting al-Qaida anywhere in the world, including in countries unable or unwilling to do it themselves, the top U.S. counterterror official said Friday.

White House counterterror chief John Brennan laid out what could be called the Osama bin Laden raid doctrine in remarks at Harvard Law School. He says under international law, the U.S. can protect itself with pre-emptive action against suspects the U.S. believes present an imminent threat, wherever they are.

That amounts to a legal defense of the unilateral Navy SEAL raid into Pakistan that killed al-Qaida mastermind bin Laden in May, angering Pakistan. It also explains the thinking behind other covert counterterrorist action, such as the CIA's armed drone campaign that this week killed a top al-Qaida operative in Pakistan's tribal areas. The Obama administration has quadrupled drone strikes against al-Qaida targets since taking office.

The Obama administration has more recently expanded drone strikes and the occasional special-operations raid into areas such as Somalia, where the government may be willing to fight al-Qaida but lacks the resources. Navy SEALs targeted al-Qaida operative Saleh Ali Saleh Nabhan in Somalia in 2009 by helicopter. The SEALs then landed to pick up his body and bury it at sea, just as bin Laden later was interred.

"We reserve the right to take unilateral action if or when other governments are unwilling or unable to take the necessary actions themselves," Brennan said.

Yet Brennan followed that by saying that does not mean the U.S. can use military force "whenever we want, wherever we want. International legal principles, including respect for a state's sovereignty and the laws of war, impose important constraints on our ability to act unilaterally."

Brennan did not explain how that constraint applied when the U.S. Navy SEALs entered Pakistani territory to go after Bin Laden without Pakistani government knowledge or permission.

He said the U.S. prefers to work with countries where the targets hide, as it does in Yemen. The Yemeni government, which allows the U.S. to fly armed drones, and other types of surveillance, pairing U.S. special operations forces with its own troops.