The US military said the soldier was killed and an Afghan soldier wounded in a gun battle on Friday while they were inspecting a weapons cache in the central province of Uruzgan.
Late on Thursday, six policemen were killed when fighters ambushed a police checkpoint on the road between Kandahar and Herat in the southern district of Navand, police said.
"This is a very bad incident which we believe was carried out by the Taliban," said Raz Mohammed Khan, a local police official.
The bodies of four policemen were burned following the attack, Khan said.
Militants linked to the former Taliban government, which collapsed following a US-led bombing campaign in 2001, have claimed responsibility for an upsurge in violent attacks on foreign and Afghan security services.
Call for dialogue
Abdul Salam Zaeef, the former Taliban ambassador to Pakistan, called on the US to negotiate with the Taliban - if it wants to bring the insurgency in Afghanistan to an end.
Zaeef has returned to Afghanistan in late 2005 after being held for more than three years at the US military prison camp at Guantanamo Bay, Cuba.
"I think the problem (of violence) is increasing and people have to decide whether they will solve it through use of power or negotiation. Afghanistan needs reconciliation but I don't think the Americans want to negotiate," he said.
Colonel Tom Collins. a US military spokesman, ruled out any dialogue with insurgents.
"We don't negotiate with terrorist organisations and the Taliban extremists have committed themselves to violence," Collins said.