Lieutenant-General Raymond Odierno said that about 80 per cent of those fighting US forces were thought to be ready to join Iraq's political process.
He said: "We're talking about ceasefires and maybe signing some things that say they won't conduct operations against the government of Iraq or against coalition forces."
"Let the people of Iraq vote if they want the US to stay or leave"
Bob Kaye, Bohemia, US
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US commanders hope to convince local Iraqi resistance groups to split from groups such as al-Qaeda in Iraq.
"We have organised ourselves to be more aggressive in this area," Odierno said.
"We believe a large majority of groups within Iraq are reconcilable, and are now interested in engaging with us."
In the western province of Anbar, tribal leaders have turned on al-Qaeda in Iraq.
And on Thursday, residents of west Baghdad reported that members of the 1920 Brigades group were fighting their former al-Qaeda allies. Al Jazeera said quoting Iraqi police sources that up to 12 armed men were killed in clashes between fighters from al-Qaeda in Iraq and Sunni fighters in Amiriya district.
The clashes caused damage to residential areas and forced many families to flee the neighbourhood.
Brigadier-General Perry Wiggins, deputy director of regional operations with the US joint chiefs of staff, admitted on Wednesday that May had been "a tough month".
He said: "We're moving into places where we haven't been, not necessarily before."