In a recent speech Gates warned that the nation's economic difficulties likely will not allow for defense spending increases sufficient to sustain the current force structure.
Reforming the defense bureaucracy to yield additional resources needed to modernise the force is now an urgent requirement, he said.
"The proverbial wall has been brought to our back," Gates said.
"What might have been considered a noble or worthy endeavour in the past is now a task that can no longer be denied or postponed."
In addition, the Pentagon chief called for increased scrutiny of requirements for big-ticket weapon systems that the services claim meet key needs without accounting for the broader inventory of Defense Department capabilities that collectively give US forces a quantitative and qualitative advantage over nearly any potential adversary.
"Before making claims of requirements not being met or alleged ‘gaps' - in ships, tactical fighters, personnel, or anything else - we need to evaluate the criteria upon which requirements are based and the wider real world context," the defense secretary said.