A retired US army general is heading to Iraq to conduct a security review as the country prepares for elections.
There are serious concerns over security for the Iraqi elections
Pentagon officials are playing down the significance of Gen Gary Luck's task, but it comes at a crucial time.
On Tuesday, the Iraqi prime minister admitted that violence would prevent some parts of Iraq voting in the election on 30 January.
Iyad Allawi spoke on a day when at least 15 people were killed across Iraq.
BBC Pentagon correspondent Nick Childs says there is renewed unease among lawmakers in Washington about the way ahead and whether the US military really has answers to what seems an ever deadlier insurgency.
INSURGENT VIOLENCE MOUNTS
11 Jan: 15 Iraqis killed in separate attacks across the country
10 Jan: Baghdad deputy police chief and son shot dead
7 Jan: Seven US soldiers killed in Baghdad bomb attack
6 Jan: Bodies of 18 Iraqis contracted to work at US base found outside Mosul
5 Jan: At least 25 Iraqis killed in three attacks in central Iraq
4 Jan: Governor of Baghdad, 14 Iraqis and five US soldiers killed in separate attacks
3 Jan: More than 20 people killed across Iraq
2 Jan: At least 23 Iraqi soldiers killed by a car bomb in Balad
Senior Pentagon officials reject notions that General Luck's mission is about an exit strategy, arguing that his trip is simply part of a normal process.
But there is no hiding the increasing toll Iraq is taking on the US military in terms of casualties, resources and morale, our correspondent says.
As the violence intensifies, the US administration is reported to be looking at new ways to tackle the insurgency.
However US Defense Secretary Donald Rumsfeld dismissed as "nonsense" a report in Newsweek magazine that Americans were considering forming hit squads to hunt down insurgent leaders.
In other developments:
- One American soldier is killed in Anbar province and three members of the Iraqi national guard killed in Mosul, the US military says
- The bodies of eight Ukrainian soldiers and one Kazakh who were killed in a blast in Iraq on Sunday are returned to Kiev
- US forces says they have detained six suspects in last week's assassination of the Baghdad governor.
More Iraqi troops
Gen Luck's particular focus will be the Iraqi security forces, which are key to any US hopes of creating a stable Iraq and reducing its own force levels, but which are clearly still a source of concern.
On Tuesday, Iraq's interim government said it has set aside $2.2bn of this year's budget to strengthen the security forces, who will be responsible for maintaining order on polling day.
Mr Allawi said it would fund an increase in the number of Iraqi troops from about 100,000 to 150,000.
"We need to equip the police and army with the new modern weaponry that will enable them to protect the country," he added.
Earlier in the day, at least six police officers died in Tikrit, seven Iraqis were killed in an attack south of Baghdad, and at least two died in a bomb in Samarra.