Insurgent attacks in Afghanistan on Sunday left four U.S. soldiers dead.
A NATO spokesman said the fighting occurred in the eastern part of the country near the border with Pakistan and in southern Afghanistan.
There have also been continued insurgent attacks on Afghan civilians. On Saturday, the brother of a candidate competing in next month's parliamentary elections was killed in western Herat province. The attack is seen as part of an insurgent campaign to disrupt the run-up to the September 18 poll.
And in southern Kandahar province, a senior member of a private security firm has been killed.
Afghan President Hamid Karzai has said he wants private security firms out of the country by the end of the year. In an interview on U.S. television, ABC's This Week with Christiane Amanpour Mr. Karzai called them a obstruction to the growth and development of Afghan security forces, particularly the county's police.
Mr. Karzai says he is reaching out to individual members of the Taliban who are not allies of al-Qaida but he says there is no formal peace process. He said peace talks could take place with Taliban officials not part of a terrorist network or foreign body. In his words, "the roadmap is clear."
The Afghan president also said the rights of Afghan women will not be sacrificed in any peace agreement with the Taliban.
Some information for this report was provided by AP and AFP.