Washington says the joint work with the patrols has led to a 60 per cent decrease in attacks in Iraq since June.
The patrols are now being increasingly targeted, especially in provinces like Diyala, where US commanders say al-Qaeda has re-grouped after being pushed out of other parts of Iraq.
US commanders also say that a ceasefire by fighters of the al-Mahdi Army, loyal to Muqtada al-Sadr, a populist Shia figure, is lowering the bloodshed in the country.
A spokesman for al-Sadr said the leader was considering extending the six-month truce after it expires in February.
The Shia leader, who led uprisings against US troops in 2004 and whose followers were later described by US commanders as their greatest threat, surprised both Iraqis and US forces when he ordered the initial six-month freeze on his group in August.
On Wednesday in Najaf, al-Sadr's spokesman, said: "Yes, there is a chance that the freeze on the Mahdi Army will be extended."
Rear Admiral Greg Smith, a US spokesman, said the US welcomed the potential extension.
"We believe that al-Sayyed Muqtada al Sadr's pledge to work in a political process and the peaceful transition is much more constructive than through violence," he said.
The son of a prominent Shia scholar killed under the government of Saddam Hussein, al-Sadr has wide influence in the Shia south and parts of Baghdad although he does not himself carry religious standing.