A US senator says assassination drone strikes have killed around 4,700 people, including civilians, a number that exceeds some independent estimates of the toll.
"We've killed 4,700," said Republican Senator Lindsey Graham, a staunch supporter of drone use, AFP reported on Wednesday.
"Sometimes you hit innocent people, and I hate that, but we're at war, and we've taken out some very senior members of al-Qaeda," Graham added.
Graham defended President Barack Obama's use of drones to carry out assassinations overseas, saying "It's a weapon that needs to be used."
"It's a tactical weapon. A drone is an unmanned aerial vehicle that is now armed," the senator noted.
US officials refuse to publicly discuss any details of the covert program and the death toll from drone strikes remains a mystery.
A report by the Washington-based New America Foundation has said that there have been 350 US drone strikes since 2004, most of them during President Obama's terms in office. The foundation has put the death toll between 1,963 and 3,293, with 261 to 305 civilians killed.
According to the London-based Bureau of Investigative Journalism, between 2,627 and 3,457 people have been killed by US drones in Pakistan since 2004, including between 475 and nearly 900 civilians.
Graham, however, did not make it clear weather the figure was the US government's own estimate of casualties from drone strikes.
The use of assassination drones overseas under the administration of Obama has caused a national debate.
Former US Secretary of Defense Robert Gates has also called for the formation of a third group to check on the president’s ability to conduct drone strikes.
"I think this idea of being able to execute, in effect, an American citizen, no matter how awful, having some third party -- informing the Congress or the intelligence committees or something like that...some check on the ability of the president to do this has merit, as we look to the longer term future," Gates said.
On February 14, Obama promised to be more forthcoming with the American public on his administration's campaign of drone strikes.
"What I think is absolutely true is it's not sufficient for citizens to just take my word for it that we're doing the right thing," Obama said in an online video question-and-answer session sponsored by Google.
He vowed to work with Congress to craft a "mechanism" to be more open about how the drone war is conducted.
Washington uses assassination drones in several countries, claiming that they target “terrorists.” According to witnesses, however, the attacks have mostly led to massive civilian casualties.