“We knew we had some of the big boys,” one source told The Washington Post. But “the process is so slow that by the time we got the clearances and everybody had put in their two cents we called it off”.

The problem was the desire within US Central Command, which co-ordinates the war effort from its Florida headquarters, to limit civilian casualties that might inflame America’s Muslim and Arab allies.

But Centcom’s attempts to limit collateral damage had served merely to prolong the war, and forced the Pentagon to insert commandos on the ground to hunt down the same targets, the officials argued in a rare sign of friction within the upper reaches of the US military.

“It is shocking the degree to which collateral damage hamstrung the campaign,” said one. General Charles Wald, who has been commanding the air campaign in Afghanistan, had registered more than a dozen complaints about the delays to General Tommy Franks, who has overall command of the military operations, but without success.

Centcom has insisted on authorising all major strikes instead of delegating that power to commanders of the air campaign based at the Prince Sultan airbase in Riyadh, Saudi Arabia. On one occasion Captain Shelly Young, Centcom’s top lawyer, reportedly refused to approve the bombardment of a military convoy moving to reinforce Taleban front lines because it was too obvious a target. He was afraid the Taleban might have put children in the convoy to trick the US into killing them.

One general also blamed micromanagement by Donald Rumsfeld, the US Defence Secretary, and his civilian aides. It was “military amateur hour”, he complained. “The worst thing is the lack of trust at the senior leadership level.”

Other sources spoke of friction with the CIA, which has fired about 40 Hellfire missiles from its unmanned Predator drone aircraft without first telling the Pentagon. A CIA spokesman insisted there had “never been a better relationship between the CIA and the military”.