The incident occurred after Mike Mullen, chairman of the US joint chiefs of staff, arrived in Kabul late Friday on a mission to reassure Afghan leaders following the sacking of General Stanley McChrystal,the commander of US and Nato troops in Afghanistan.
During his one-day visit, Mullen was expected to explain the circumstances leading up to McChrystal's dismissal and reassure Hamid Karzai, the Afghan president, that a change of leadership did not mean a change of tactics.
"My message will be clear. Nothing changes about our strategy. Nothing changes about the mission," Mullen said at a news conference in Washington before his departure for Afghanistan and Pakistan.
General David Petraeus has been appointed as the new commander,a move that Robert Gates, the defence secretary, said was the "best possible outcome to an awful situation".
Speaking at the same news conference on Thursday as Mullen, Gates said there was progress in the Afghan war - the administration's latest bid to defend the mission as foreign troop casualties hit record highs.
Nato announced overnight the death of another alliance soldier following an rebel attack in eastern Afghanistan, bringing to three the number killed on Friday.
June has become the deadliest monthof the war since it began in late 2001, with 84 foreign troop deaths.
This year 304 foreign soldiers have been killed - already the second highest annual total in the war - under McChrystal's strategy to send tens of thousands of extra troops into Afghanistan.
There are 140,000 troops in Afghanistan, with the number set to peak at 150,000 by August, with a surge of efforts in the southern province of Kandahar, the Taliban's heartland.