There are growing signs that the US is increasingly turning to a new tactic in facing the Sunni-led insurgency in Iraq.
By Jim Muir
BBC News, Baghdad
The US military is arming Sunni groups to secure their own areas
On Sunday, US military commanders and Iraqi provincial officials held a meeting with 130 Sunni tribal sheikhs in Saddam Hussein's old hometown of Tikrit.
According to the US, the tribal leaders reached a "historic agreement" to play a more active role in defending their troubled province, Salahuddin, against al-Qaeda and other radical insurgent groups.
It is the latest move in what is clearly becoming one of the main thrusts of the US exit strategy here - to empower and arm Sunni Arab tribes and factions, provided they pledge to resist outside militants like al-Qaeda.
One of the top US military commanders, Maj-Gen Rick Lynch, confirmed the US was moving in the direction of training and arming Sunni groups to secure their own areas, often under the mantle of the Iraqi police force.
"There are tribal sheikhs out there who say: 'Hey, just allow me to be the local security force. I don't care what you call me. You can call me whatever you want. Just give me the right training and equipment and I'll secure my area.' And that's the direction we're moving out there," Gen Lynch said.
[Al-Qaeda in Iraq's] uncompromising brand of extreme fundamentalist Islam has apparently begun to alienate the more nationalist Iraqi strands of the insurgency
US commanders on the ground have been authorised and encouraged to enter into truces and agreements with local Sunni factions wherever possible, even if they are suspected of using arms against US forces in the past.
It is a tactic that is deemed to have worked successfully in the western province of al-Anbar, where Sunni tribes have increasingly clashed with al-Qaeda and its allies.
Al-Anbar was until recently a synonym for "insurgent hotbed", but US commanders have reported a marked drop in violence since many of the province's Sunni tribes signed up with the government and encouraged their followers to join the local police.
Some police recruiting posts in al-Anbar were also attacked by al-Qaeda-linked insurgents, further fuelling local resentment against them.
The insurgency has always been made up of multiple strands.
The US and Iraqi governments have always regarded the groups such as al-Qaeda in Iraq as being irreconcilable and beyond the pale, and they still do.
Variously known as jihadis or salafis, many of the groups' fighters and suicide bombers are believed to be Islamist radicals from outside the country.
Their uncompromising brand of extreme fundamentalist Islam has apparently begun to alienate the more nationalist Iraqi strands of the insurgency, some of them former Baathists, others just Sunnis with a grudge against the US-led coalition and a government they feel ill represents their interests.
However, a recent statement from the al-Qaeda-linked Islamic State in Iraq sought to cast doubt on the extent to which the tribes had turned against it.
It thanked tribal leaders for "assisting and supporting the mujahideen in their confrontation with the Crusaders and rejecting some who sold their religion and people at a very cheap price".
The US military surge is suffering from Iraqi police failures
The group said "dozens of pledges from the chiefs and noblemen of the tribes have been received by us".
It said that tribes "even after four years of fighting and killing, continue to offer their children [and] provide shelter for the mujahideen".
However, there has been conflict between the Islamic State in Iraq and the Islamic Army of Iraq, a more local nationalist Sunni faction, for control of the Amariya district in south-west Baghdad.
The two sides, former allies against the US presence, agreed to a truce, though the underlying tensions remain.
The US decision to turn increasingly to local security is a tacit admission that, in at least some areas, the policy of relying on the Iraqi armed forces and police simply has not worked.
Those institutions are riddled with problems.
It has proven hard to find seasoned officers to take the lead. Sectarianism and penetration by militias are rampant, especially in the police.
US military officials admit the current Baghdad troop "surge" is suffering from the fact that the Iraqi police have not proven to be up to the task of holding areas secured by the push.
Empowering Sunni tribes and groups to look after their own security may prove to be part of the solution - though it will not solve all the country's problems by any means.