There is a significant risk that the US military will not be able to quickly and fully respond to another crisis due to its commitments in Iraq and Afghanistan, according to a report to the US Congress.
The assessment, done by the nation's top military officer, Gen Peter Pace, chairman of the Joint Chiefs of Staff, represents a worsening from a year ago, when that risk was rated as moderate.
A report that accompanied the review concluded that although the Pentagon is working to improve its warfighting abilities, it "may take several years to reduce risk to acceptable levels".
Gen Pace's report comes as the US is increasing its forces in Iraq to quell escalating violence in Baghdad.
The review grades the military's ability to meet the demands of the nation's military strategy - which would include fighting the wars as well as being able to respond to any potential outbreaks in places such as North Korea, Iran, Lebanon, Cuba or China.
The latest review by Gen Pace covers the military's status during 2006, but the readiness level has seesawed back and forth during the Iraq war. Officials, speaking on condition of anonymity because the risk levels are classified, said the risk for 2005 was moderate, but it was assessed as significant in 2004.
His assessment was submitted to US defence secretary Robert Gates at the beginning of this year, and so does not reflect the latest move to pour 21,500 more troops into Iraq over the next few months.