The CIA and other spy agencies are scrambling to close intelligence gaps as they seek ways to support possible military or covert action against the leaders of the al-Qaeda-inspired militant group that has seized parts of Iraq and threatens Baghdad's government.
The lack of clear intelligence appears to have shifted President Barack Obama's immediate focus away from airstrikes in Iraq because officials said there are few obvious targets.
However, officials said no final decisions had been made and suggested Obama ultimately could approve strikes if strong targets do become available.
As the US intensifies its intelligence collection efforts, officials are confronting a diminished spying capacity in the Middle East, where the 2011 departure of US troops and the outbreak of civil war in Syria left large swaths of both countries largely off-limits to American operatives.
US intelligence analysts are working to track the movements of key figures in the militant group known as the Islamic State in Iraq and the Levant, which seized Mosul, Tikrit and other towns in Iraq as the country's military melted away.
They are sifting through data provided by Jordanian, Saudi, Turkish and other intelligence services, as well as their own human sources, satellites, drones and communications intercepts by the National Security Agency, US intelligence officials say.
The officials would not be quoted by name because they were not authorized to discuss the classified details publicly.
Obama planned to brief top congressional leaders on his administration's possible responses to the crumbling situation in Iraq during a White House meeting today.
The Obama administration has discussed the possibility of launching targeted airstrikes, either with drones or manned aircrafts, to try to blunt the momentum of the fast-moving Sunni insurgency.
Other options under consideration include deploying a small contingent of US special operations forces to help train the Iraqi military and boosting intelligence available to the Iraqis.
More broadly, the Obama administration is also pressing for Iraqi Prime Minister Nouri al-Maliki to take steps to make his Shiite-dominated government more inclusive.
