With the Iraq war over and U.S. forces preparing to leave Afghanistan, Deputy Secretary of Defense Ashton Carter said last year the Asia-Pacific region was "one of the most prominent and important" issues for the Pentagon.
Donilon emphasized the point by saying it "was clear that there was an imbalance in the projection and focus of U.S. power" in the region, the Pentagon's news agency quoted him as saying.
He stressed, however, that the pivot wasn't just a military doctrine but one that includes trade, investments and political engagement.
"We need open and reliable channels to address perceptions and tensions about our respective activities in the short-term and about our long-term presence and posture in the Western Pacific," he said.
Last year, Seth Jones, an analyst at policy center Rand, said "pivot" meant overlooking an evolving al-Qaida in the Middle East and North Africa.