President Obama's counter-terrorism adviser has given the most detailed explanation so far of America's use of drones to kill members of al-Qaeda.
In a speech to a Washington think tank, John Brennan said the strikes were helping to win the war on the militant network.
President Barack Obama wanted to be more open about the practice, Mr Brennan added.
The comments come in the week marking a year since Osama Bin Laden's death.
BBC Washington correspondent Paul Adams says this is not the first time the Obama administration has confirmed the use of drone strikes.