The United States Attorney General tells Channel 4 News US drone strikes in Pakistan, which have killed 900 people in the last year, are "totally consistent with international law".
It is estimated as many as 2,283 people have been killed by US military drones in Pakistan since 2004.
And in the last year alone, a Channel 4 News investigation uncovered figures which suggested that 500 to 900 militants have been killed by drones near Pakistan's border with Afghanistan.
The number of attacks is double the number conducted in the preceding year and by far exceeds the number of drone strikes conducted under the Bush regime.
Experts have questioned the legality of the strikes in Pakistan, a country with which the United States is not at war - but the US maintains the strikes are necessary to mitigate the threat of al-Qaeda and the Taliban.
One lawyer, representing the families of some of those who have been killed by drones in Pakistan, told Channel 4 News that the attacks were the "next Guantanamo".
Read more in the Channel 4 News Special Report on drone warfare in Pakistan
But speaking to Channel 4 News, US Attorney General Eric Holder said that the use of drones was "totally consistent" with the law.
He said: "The use of the techniques that we employ is totally consistent with international law, approved and reviewed by the legal authorities within the US.
"Anybody who is the target of any of our military action is always thought to be somebody who is thought to be a threat to the US, so there is a basis to any of the action we take, on the battlefield, in the variety of ways that we do it."
He said members of his department reviewed any military action taken by the US before it begins.
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22 December 2010