US confirms four American citizens killed by drones
23 May 2013 Last updated at 04:56 BST
The US justice secretary has acknowledged that four Americans have been killed abroad in drone strikes since 2009.
Eric Holder said only one individual had been specifically targeted - the radical cleric Anwar al Awlaki, who was killed in Yemen in 2011.
President Barack Obama is due to make a major speech on counter-terrorism on Thursday, laying out the thinking behind drone strikes, and the legal arguments.
Rajini Vaidyanathan reports.