The Obama administration is considering expanding its support to Iraqi forces as they fight off a renewed al Qaeda threat, but Washington's ability to significantly increase security assistance to Baghdad will remain limited.
US officials say they are in discussions with the Iraqi government about training its elite forces in a third country, which would allow the United States to provide one modest measure of new assistance against militants in the absence of a troop deal that allows US soldiers to operate within Iraq.
No further details were immediately available about where that might take place or how many troops it might involve.
Reluctance to further empower Prime Minister Nuri al-Maliki or put American boots on the ground constrains US support for Iraq as it battles militants from the Islamic State of Iraq and the Levant, an al Qaeda affiliate, in Anbar province, and seeks to reverse a striking surge in violence across the country in the last year.
The United States is sending missiles, surveillance aircraft and other gear that may help Iraqi forces rebuff al Qaeda in the western province, a Sunni Muslim stronghold.
But Washington also wants Maliki, a Shi'ite, to do more to reach out to minority Kurds and Sunnis who accuse him of fanning sectarian tensions.
The conflict in Anbar is the latest in a string of events pitting Maliki against Iraqi Sunnis, many of whom resent the Shi'ite domination that has followed the US-led ouster of Sunni leader Saddam Hussein in 2003.
Colin Kahl, a former senior Pentagon official specializing in the Middle East, said the US military's ability to conduct overt activities in Iraq was extremely limited, but that the Obama administration was likely providing the Iraqi government with intelligence to help them target al Qaeda.
"As we do so, we have to be mindful that we are not empowering Maliki's bad behavior, and we need to be careful not to do anything that makes it look like we are taking sides in a sectarian fight," Kahl said.
Beyond such modest support, and despite growing USfears that the war in Syria is fuelling a regional al Qaeda comeback, US officials say their hands are largely tied in Iraq.
Secretary of State John Kerry made clear last weekend the Obama administration has no appetite for sending US troops back.
"This is a fight that belongs to the Iraqis," he said. "We're not contemplating putting boots on the ground. This is their fight, but we're going to help them in their fight."
And without a Status of Forces Agreement, which provides a legal underpinning for stationing US soldiers overseas, the United States can hardly conduct overt military activities in Iraq.
Maliki, too, would be loathe to be seen inviting back US troops whose presence many Iraqis saw as an occupation force.
Since 2011, when the Obama administration abruptly pulled US soldiers from Iraq after failing to reach a troop deal with Maliki's government, the upheaval of the Arab Spring and the war in Syria have helped push Iraq from the center of U.S. foreign policy discussions.
As the Pentagon seeks to wind down the war in Afghanistan, and Kerry pursues diplomatic deals to address Iran's nuclear ambitions and the Israeli-Palestinian dispute, increasing bloodshed in Iraq has not altered that calculus.
The reluctance of the Obama administration - and of Maliki himself - to revisit the years of US military involvement in Iraq has dramatically curtailed U.S. influence there.
Since the departure of US forces in 2011, the Office of Security Cooperation-Iraq, attached to the US embassy in Baghdad, has become the anchor of US security assistance for Iraq. At least 100 Pentagon employees there oversee military sales to Iraq and advise Iraqi ministries.
But some covert activities can take place. The Iraqi government invited US special forces to return to provide counterterrorism and intelligence support to local forces, according to a report in The New York Times.
Some in the US Congress, including influential lawmakers such as John McCain, warn of Maliki's autocratic tendencies and close ties with Iran.
They complain he has continued to allow Iran to send military assistance to Syrian President Bashar al-Assad across Iraqi airspace and has not lived up to promises to protect Iranian dissidents in Iraq.
Ken Pollack, a former White House and intelligence official who was a leading advocate for the 2003 war with Iraq, said the current US focus on the return of al Qaeda, with its possible intent to strike the West, overlooked the true sectarian and political roots of recent conflict in Iraq.
"Sending weapons isn't going to fix the problem," he said. "It's going to force the Maliki government to rely on force."
Pollack and others have urged the administration to condition security assistance on conciliatory steps by Maliki, perhaps by bringing in minority leaders into his government.
After Maliki made a plea for increased military sales in a visit to Washington in November, the administration has been working to speed up delivery of military equipment, including Hellfire missiles and surveillance aircraft.
An Iraqi request for Apache attack helicopters has not yet moved forward, largely because of congressional concerns. Congress has approved the sale of F-16 fighters to Iraq, but they are not expected to be delivered until fall.