US general makes pledge to family of dead aid worker

US General David Petraeus, in London for talks with senior political and military leaders, said he had spoken to Ms Norgrove's father, John, to offer his condolences for her death during an attempted rescue by American special forces.

He said he found it "disturbing" that the original account of the raid – which claimed she had been killed by her Afghan kidnappers – had apparently proved incorrect. However, speaking at the Royal United Services Institute think-tank in London, he said that it was important not to "jump to conclusions" until the inquiry had established exactly what happened.

"This morning I talked with Mr Norgrove and conveyed to him not only the most sincere condolences but also an update on the investigation that is ongoing," he said.

"We will investigate to determine the specific facts in a joint, completely transparent, US-UK effort that will then be shared completely with the Norgrove family as soon as the results are established."

He said that it was only realised that Ms Norgrove may have been killed inadvertently by the US forces after surveillance video footage of the raid was played through a hard-drive, producing a sharper image.

"From that, it was very clear there was a throw-in motion and an explosion that followed that, and that a grenade had been deployed," he said.

Gen Petraeus also disclosed that an AC-130 Spectre gunship had been operating in the area and that it had killed two insurgents as they tried to flee.

He said the investigation was being headed by a two-star US officer and a one-star British officer – both with extensive experience of special forces operations – and was being conducted from "outside theatre" to ensure its integrity.

The next step would be for a post-mortem examination in the UK to establish the cause of death.

After US Secretary of State Hillary Clinton expressed concern about looming defence cuts in the UK, Gen Petraeus said he had been assured by David Cameron of Britain's commitment to the Afghanistan mission. "I have repeatedly received assurances that the support for Afghanistan is iron clad, that it is 'fenced' if you will, and it will be forthcoming," he said.

However, the senior Nato civilian representative Mark Sedwill warned that comments by political leaders about when international troops might withdraw were damaging to the mission.

"Having lots of leaders around the alliance naming different dates is, from our perspective, not helpful," he said.

"Clearly it is confusing for the Afghans who we work with, it unsettles them. And of course, it reinforces among the opponents of a legitimate Afghan state that if they just hold on we will be gone."

Mr Cameron is among the alliance leaders who said he wants to withdraw by 2015.

Mr Sedwill, a former British ambassador to Kabul, said the UK position was "exactly in line" with Nato which was focussing on 2011, when the transition to Afghan control will begin.