Two US soldiers have been killed in a roadside explosion in south-eastern Afghanistan, the US military has said.
The explosives were detonated as a convoy passed by in Paktika province on Friday. A third soldier and an Afghan interpreter were wounded.
Nearly 150 US troops have now been killed in Afghanistan since the start of the US intervention in late 2001.
No one has yet said it carried out the attack but the Taleban has stepped up its campaign after a winter lull.
In a separate clash, at least two suspected Taleban fighters were killed after ambushing a police convoy in Zabul province, officials said.
The convoy was returning from the village of Gayan in Urgun district when it was attacked.
Gen James G Champion of the US forces in Afghanistan said: "Our hearts and prayers go out to the families of these two brave individuals who gave their lives so that Afghanistan might have a safe and secure future."
There are about 18,000 US-led foreign troops in Afghanistan tracking al-Qaeda and Taleban militants.
The military and the insurgents have been involved in a number of heavy clashes, particularly in the south and east, over the past few months.