Justifying the use of remotely piloted aircraft, a top Obama administration counter-terrorism official said that "rigorous standards" were applied in these attacks which were carried out in a "surgical manner" with "laser like precision."
Marking the anniversary of the killing of Al Qaeda founder Osama Bin Laden [ Images ] by American Special Forces in Pakistan, John Brennan, President Barack Obama's [ Images ] top counter-terrorism adviser, told a meeting in Washington, DC that the strikes were used only in cases of "significant threat."
He described Al Qaeda as "legitimate military target" which was in armed conflict with the US.
"There is nothing in international law that bans the use of remotely piloted aircraft for this purpose or that prohibits us from using lethal force against our enemies outside of an active battlefield," Brennan said in his address to international scholars at Woodrow Wilson Centre.
This is the first time that US has made public an elaborate explanation of drone strikes which have sharply increased in places like Pakistan and Yemen with the emergence of new technology.
Brennan said the President had directed officials to be more open about how they decide to kill terrorism suspects.
"These targeted strikes are legal," he asserted.
"To briefly recap, as a matter of domestic law, the Constitution empowers the President to protect the nation from any imminent threat of attack," the US official said.
"The Authorisation for Use of Military Force -- the AUMF -- passed by Congress after the September 11 attacks, authorises the President 'to use all necessary and appropriate force' against those nations, organisations and individuals responsible for 9/11. There is nothing in the AUMF that restricts the use of military force against Al Qaeda to
Afghanistan," he said.
"We only authorise a strike if we have a high degree of confidence that innocent civilians will not be injured or killed, except in the rarest of circumstances," he said.
The killing of civilians by drones has fuelled immense anti-American sentiment, especially in Pakistan. The number of such deaths -- especially in remote regions where it is difficult for neutral observers to investigate -- has been hotly disputed. American officials have described such deaths as rare, while critics have said there are far more than the government acknowledges.
Brennan said American citizens who join Al Qaeda may also be targeted, but he did not mention the killing of at least three Americans in drone strikes in Yemen last year, including Anwar Al-Awlaki, a radical cleric.
Brennan listed four organisations that the United States government now considered to be part of the war against Al Qaeda: the "core" Al Qaeda, whose leadership he described as "a shadow of its former self"; two of its affiliates in Yemen and in North and West Africa; and the Shabab militia in Somalia, although he described it as being "in decline" and mainly focused on parochial concerns.
He also said the United States was monitoring the emergence in Nigeria of the group Boko Haram, which "appears to be aligning itself with Al Qaeda's violent agenda," but he stopped short of calling it an "affiliate" of Al Qaeda.