The top US general in Iraq says the military alone cannot provide a solution to the country's conflict.
Gen David Petraeus said it was critical that alienated groups be brought into talks. He also said he believed violence in Baghdad could be curtailed.
He was speaking after the US defence secretary approved an extra 2,200 military police to aid the crackdown.
However, Democrats in the US Congress have proposed legislation requiring all US troops to leave Iraq by August 2008.
It is a direct challenge to President George W Bush, who has ruled out any fixed end to the Iraq operation.
Democrats, who took control of Congress after November elections, say they want the measure tied to the $100bn (£52bn) the president has requested to continue funding the wars in Iraq and Afghanistan.
Gen Petraeus said improving the situation in Iraq required more than armed force.
"There is no military solution to a problem like that in Iraq, to the insurgency of Iraq," he said.
"Military action is necessary to help improve security... but it is not sufficient. There needs to be a political aspect."
He said some groups "who have felt the new Iraq did not have a place for them" would have to be engaged in talks.
The new Baghdad offensive involves US and Iraqi forces, thousands of whom are already on the ground, sweeping the city for militants and illegally held weapons.
Gen Petraeus said: "It's too early to discern significant trends, but there have been a few encouraging signs."
However he admitted "sensational attacks inevitably will continue".
Options running out
BBC defence and security correspondent Rob Watson says that despite the scale of the new Baghdad drive, there simply are not enough US troops to prevent the violence shifting to other areas.
Our correspondent says that privately US officials believe it will not be possible to judge whether the surge has worked until all the troops have arrived in the summer and, if it does not, there will be few options remaining.
Gen Petraeus said it was essential to tackle the sectarian violence that has flared between Sunni and Shia Muslims since an attack on a key Shia shrine in Samarra just over a year ago.
He said US and Iraqi forces must "control the demons responsible for the vicious sectarian violence of the past year - demons who have torn at the very fabric of Iraqi society".
Gen Petraeus said sensational attacks would inevitably continue
The general detailed the measures taken jointly by US and Iraqi forces to secure Baghdad's neighbourhoods.
He said the aim was not just to secure areas of the capital, but to hold them and help to improve the provision of basic services.
The general also denounced as "thugs with no soul" the recent attackers of Shia pilgrims. On Tuesday, more than 100 people died when suicide bombers targeted a crowd of pilgrims in the town of Hilla.
On Wednesday US Defence Secretary Robert Gates approved the general's request for an extra 2,200 military police to support the security drive in Baghdad.
Mr Gates said the deployment would be in addition to the nearly 24,000 combat troops and support personnel approved by President George W Bush.