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.
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