August was the first month since the US-led invasion in 2003 that no US soldiers were killed in Iraq.
An independent group, icasualties.org, has displayed the statistics for August on its website, which tracks US fatalities in Iraq every month.
US Col Douglas Crissman said it showed how far Iraqi security forces had come.
Figures for Iraqi civilian and security forces deaths in August are not yet available, but the month has seen major attacks with substantial loss of life.
On 28 August a suicide bombing at a major Sunni mosque that killed 32 people in Baghdad and a series of coordinated assaults on 15 August killed at least 60 people.
'No hostile deaths'
The 48,000 US troops still in Iraq will withdraw at the end of the year. Almost 4,500 US soldiers have died there.
Col Crissman, who is in charge of American forces in four provinces of southern Iraq, told the New York Times: "If you had thought about a month without a death back during the surge in 2007, it would have been pretty hard to imagine because we were losing soldiers every day, dozens a week."
The AFP news agency quoted US Major Angela Funaro as saying: "August was the first month with no hostile deaths and no non-combat deaths, which includes accidents or illness.
"However, there were two other months on record - December 2009 and 0ctober 2010 - when the United States Forces-Iraq had no hostile deaths, but at least one non-combat-related death."
All US troops still in Iraq must pull out by the end of the year, under the terms of a 2008 security pact.
However, Iraqi politicians announced in early August that they would begin talks with Washington over a military training mission to last beyond 2011.
Iraqi Health Ministry statistics suggest 1,449 civilians died in violence in the 11 months from 1 September of last year to the beginning of August.
During the same 11 months, 543 Iraqi police and 379 soldiers were killed, according to figures from the interior and defence ministries, reported by Reuters news agency.