A US attack killed 19 insurgents and 15 civilians, including nine children, in Iraq - one of the heaviest civilian death tolls in an American operation in recent months.
The military said it was targeting senior leaders of al-Qaida in Iraq.
American forces have applied fierce and determined pressure on militants, especially al-Qaida in Iraq, since the full contingent of additional US troops arrived on June 15.
But Prime Minister Nouri Maliki has recently confronted top American commander General David Petraeus about what he sees as overly aggressive US tactics that harm innocent civilians, according to Iraqi officials.
The military statement detailing yesterday's air and ground assault said soldiers were acting on intelligence reports about an al-Qaida meeting in the Lake Tharthar region.
The southern reaches of the man-made lake are about 50 miles (80 kilometres) northwest of the capital Baghdad.
The American account said US surveillance confirmed "activity consistent with the reports and supporting aircraft engaged the time-sensitive target".
The first air attack killed "four terrorists", said the statement.
The military said it then tracked some of those who escaped the initial attack to a place south of Lake Tharthar.
It said ground forces moved on the site and came under fire. Air support was called in.
"After securing the area, the ground force assessed 15 terrorists, six women and nine children were killed," the statement said.
Two suspected al-Qaida members, a woman and three children were wounded, according to the military account.
The military said its troopers "were reviewing information from the scene (of Thursday's attack) as well as assessing the level of damage involved".
The statement also issued regret "that civilians are hurt or killed while Coalition forces search to rid Iraq of terrorism".
On October 5, a pre-dawn US raid on Khalis, a Shiite city north of Baghdad, killed 25 people when US troops called in airstrikes after meeting a fierce barrage while hunting suspected smugglers of arms from Iran to Baghdad.
Village leaders said the victims included civilians, but the military insisted the 25 killed were militants.
US forces have chalked up notable success against militants, but the government has become nearly deadlocked and made no progress on healing wounds among Iraq's sectarian and ethnic groups.
The US military announced the combat death of a soldier on Wednesday in eastern Baghdad.
At least 35 Iraqis were killed or found dead in attacks nationwide yesterday, as suicide car bombers struck a market in the northern city of Kirkuk and a cafe in eastern Baghdad.
Also yesterday, the US military revealed that rockets fired from a nearby abandoned school struck Camp Victory, US military headquarters near Baghdad Airport, killing two members of the US-led coalition and wounding 40 other people on the sprawling headquarters for US forces in Iraq.
Most troops stationed at the base are American but there are small contingents from other countries.
The military said those wounded in Wednesday's attack included two "third-country nationals", meaning they were not Americans or Iraqis.