No other details about Sunday's casualty were given in accordance with standard procedure. The death was the fifth among U.S. troops in Afghanistan in September, following the deaths of more than 220 American troops over the past three months.
This year is already the bloodiest for American forces in Afghanistan since the 2001 invasion, with at least 321 killed so far.
Violence is increasing with an infusion of 30,000 additional U.S. troops that brings the total number of foreign forces in Afghanistan to more than 140,000, along with stepped-up operations ahead of next week's parliamentary elections.
The Taliban vowed Sunday to attack polling places opening for the Sept. 18 vote and warned Afghans not to participate in what it called a sham election.
The threat issued Sunday followed the announcement of a final list of polling places to be opened around the country.
"It is only to the benefit of foreigners who want to maintain their existence in the country by holding such a process and we believe that the people will not get any benefit out of it," Taliban spokesman Zabiullah Mujahid told The Associated Press in a telephone interview.
"That's why we announced to the local people that all Afghan people should boycott this election and they should not participate on the polling date," Mujahid said.
The Taliban's position was consistent with those it has taken in the past. The insurgents seek to topple the government in Kabul and drive foreign troops from the country, and have boycotted or sought to sabotage all aspects of the political process.
Taliban threats and intimidation drove down voter turnout in last year's fraud-marred presidential election, especially in rural areas where security is harder to ensure, and many Afghans this time say they won't vote for fear of attacks.
Election officials plan to open 5,897 voting sites, having discarded more than 900 locations because of security concerns. Last year, 6,167 voting centers nominally operated.
Voters will choose 249 members of the lower house of parliament from more than 2,500 candidates, including dozens of women.
Afghanistan's government and its foreign partners say they hope the elections will further consolidate the country's shaky democracy and put it on a path toward long-term political stability, allowing the withdrawal of the roughly 140,000 NATO-led foreign troops in the country.