By Paul Anderson
BBC correspondent in Kabul
US military commanders in Afghanistan have cast doubt on claims by Afghan officials that they accidentally killed eight civilians in their ongoing anti-Taleban operation in the south.
On Saturday, the governor of Zabul province said eight nomads had been killed in their tent by a bomb dropped by an American helicopter chasing Taleban fighters.
A new US anti-Taleban offensive is under way
The governor said the fighters were pinpointed when a signal from a satellite phone they were using near the tent housing the nomads was picked up.
But in a joint taskforce press statement on Sunday, the Americans said that they had killed a Taleban commander and a fighter they were chasing, and were confident that no-one else was killed.
"Based on the available reliable information at this time, we are highly confident only combatant anti-coalition persons were killed or wounded during the Wednesday engagement," the statement said.
This is the latest in a series of what is known as friendly fire incidents.
In one incident last year American forces killed at least 48 civilians, when a stray bomb hit a civilian area in the southern province of Uruzgan.
Twenty-five of the dead were from a single family attending a wedding.
After an investigation the Americans said they had been fired upon by the Taleban and had retaliated.
The danger for the coalition is that such dwindling support as its forces have among Afghans could evaporate when news of civilian deaths breaks.
The Americans need the support of local people and warlords in the continuing hunt for Taleban and al-Qaeda fighters and their sympathisers.
They say their three-week operation, codenamed Mountain Viper, to chase and kill hundreds of regrouping fighters, has been a success.
The Americans say around 150 have died, among them several Taleban district and provincial commanders.
The Taleban - in the rare statements they make - say the figures are nothing like that.
Over the past few months the Taleban have staged increasingly bold and frequent attacks against Afghan forces backing up the coalition, as well as foreign aid workers and Afghans working for them.
One leader was recently reported as saying they would continue their jihad, or holy war, until the Americans are driven from Afghanistan.