A number of US special operations troops have been killed or wounded in fighting in southern Afghanistan, Defence officials said.
The fighting today against the Taliban was near the city of Marja in Helmand province, where the Taliban has made recent gains.
Details on the battle and the number wounded or killed is unclear.
One US official said a US helicopter was sent to the scene to evacuate casualties but did not immediately take off because a mortar landed nearby.
It was not clear whether the mortar has damaged the helicopter.