WASHINGTON: The deadly U.S. campaign of drone strikes against al Qaeda is  fully legal under international law, President Barack Obama's counterterrorism chief insisted on Monday in the most extensive justification of a controversial tactic that has eliminated some of the most-wanted militants.  

Speaking on the eve of the one-year anniversary of the U.S. killing of Osama bin Laden in a raid in Pakistan, the White House aide, John Brennan, said the U.S. administration holds
itself to a "rigorous" review process in deciding on drone targets in Afghanistan and elsewhere.  

The bin Laden commando raid and unmanned air strikes in Pakistan have severely strained relations between Washington and Islamabad.  

"I'm here today because President Obama has instructed us to be more open with the American people about these efforts," Brennan said in a speech to a Washington think tank.  AGENCIES