Violent civilian deaths in Iraq fell to 3,976 this year, according to a monitoring group.
But the relatively small reduction shows an "impassable minimum" may have been reached and suggests conflict in the country "will continue to kill civilians at a similar rate for years to come", the independent Iraq Body Count (IBC) said.
The civilian death toll is the lowest since the 2003 US-led invasion, down 15% from 4,680 in 2009.
But the year-on-year reduction has slowed down since the number of deaths showed a dramatic drop from 24,677 in 2007 to 9,245 in 2008.
"While any reduction in the violence rate is welcome, the slowdown in reductions is indicative of an impassable minimum that may have been reached," IBC said in their annual report.
"Taken as a whole and seen in the context of immediately preceding years, the 2010 data suggest a persistent low-level conflict in Iraq that will continue to kill civilians at a similar rate for years to come."
The trend within 2010 was described as "somewhat more hopeful".
After the US end of combat mission on August 31 there was "an immediate halving in the number of civilian deaths between August and September".
"Lowered levels have continued into the winter months," the report said.
"It remains to be seen whether this improvement will persist into 2011."