Outgoing U.S. Defense Secretary Robert Gates says the North Atlantic Treaty Organization, or NATO, faces a "dim, if not dismal future."
Gates made his final policy speech as Pentagon chief to NATO member nations in Brussels, Belgium, Friday morning.
The U.S. and European nations formed NATO in 1949 as a defense against the Soviet Union after World War II. Some have questioned the organization's usefulness since the Soviet Union collapsed.
Citing the wars in Libya and Afghanistan, Gates harshly criticized European nations' unwillingness and inability to adequately support those missions.
He said NATO is "falling down on the job" and putting too much of the burden on the U.S.
"The blunt reality is that there will be dwindling appetite and patience in the U.S. Congress - and in the American body politic writ large - to expend increasingly precious funds on behalf of nations that are apparently unwilling to devote the necessary resources or make the necessary changes to be serious and capable partners in their own defense," the U.S. defense secretary said.
Gates, a career CIA officer who rose to become the spy agency's director from 1991 to 1993, is retiring on June 30, after 4 1/2 years as Pentagon chief. His designated successor, Leon Panetta, is expected to take over July 1.
"Future U.S. political leaders - those for whom the Cold War was not the formative experience that it was for me - may not consider the return on America's investment in NATO worth the cost," he told a European think tank on the final day of an 11-day overseas journey.