| The use of drones to target al-Qaeda and Taliban leaders in Pakistan has been a contentious issue [EPA]
US officials have strongly rejected allegations in an independent UK study that a covert drone war in Pakistan has killed large numbers of civilians, saying the numbers are "way off the mark".
On Friday, US officials criticised the London-based Bureau of Investigative Journalism report's finding that there had been many more CIA attacks on alleged al-Qaeda and Taliban targets and far more civilian deaths than previously reported.
The report said that bombing raids by unmanned aircraft had killed up to 168 children in Pakistan over the last seven years.
"The numbers cited by this organisation are way off the mark," said a senior US official, who spoke to the AFP news agency on condition of anonymity.
"In the past year, in the neighbourhood of 600 militants - including more than two dozen terrorist leaders - have been taken off the battlefield.
"In that same period of time, we can't confirm any noncombatant casualties," the official said.
A second US official, who also asked not to be identified, dismissed the report as unfounded, saying: "The numbers are wrong."
The officials said intelligence agencies took precautions to avoid killing civilians and that the robotic aircraft - equipped with missiles, video cameras and sensors- can linger over a target to ensure accuracy.
"This is a weapon - fuelled by good intelligence - that allows us to counter an urgent and deadly threat in otherwise inaccessible places," said the first official.
"And it's far more precise than conventional ground operations. What's the alternative to this kind of rigour, assuming the United States and its allies are unwilling to allow al-Qaeda and its friends to plot and murder freely?"
The London-based group said 291 CIA drone strikes had taken place in Pakistan since 2004, eight per cent more than previously reported, and that under President Barack Obama there had been 236 - one every four days.
But the official said the report's numbers had not been confirmed.
"Credible reports of civilian deaths are taken into account, period. If large numbers of innocent people were being killed, the Pakistanis wouldn't stand for it. Neither would we. That's the reality," the official said.
US officials also cast doubt on one of the report's sources, Mirza Shahzad Akbar, a Pakistani lawyer who is suing the Central Intelligence Agency on behalf of civilians who say they lost loved ones in drone strikes.
"One of the loudest voices claiming all these civilian casualties is a Pakistani lawyer who's pushing a lawsuit to stop operations against some of the most dangerous terrorists on the planet," the official said.
"His publicity is designed to put targets on the backs of Americans serving in Pakistan and Afghanistan. His agenda is crystal clear."
The official said there were concerns about the lawyer's possible links with Pakistani intelligence, as Akbar had publicly named the CIA's undercover station chief in the country.
Al Jazeera is not responsible for the content of external websites.