US Defence Secretary Robert Gates has announced a review of the Fort Hood shootings to examine if the military had missed warning signs or remained "vulnerable" to similar assaults.
The 45-day review would look at possible "lapses or problems" before this month's army base shooting that killed 13 people and "what can we do to prevent something like this from happening again", Mr Gates said.
"We do not enter this process with any preconceived notions," he said.
"However, it is prudent to determine immediately whether there are internal weaknesses or procedural shortcomings in the department that could make us vulnerable in the future."
The probe will be led by former US Army secretary, Togo West, and former chief of naval operations, Admiral Vernon Clark.
An army psychiatrist, Major Nidal Hasan, has been charged with the murder of 13 people in the November 5 rampage at Fort Hood in Texas, in which 42 people were also wounded.
US Attorney General Eric Holder said yesterday he found contacts between the alleged gunman and the Yemeni cleric "disturbing".
The issue of Hasan's "contacts" gained fresh import this week as the cleric "blessed the act" and said the deadly shooting was "permissible" under Islam.