"Actually I think this will be an area where there will be a strong and positive legacy in the future," he told a high-level security forum in Singapore six months before the US presidential elections.
Gates said there was a "significant improvement" in the US-Japanese and US-Indian relationship under Bush.
"The administration has fostered a degree of collaboration with a variety of partners in Asia," Gates said at the forum, involving defence and military officials and security experts, known as the Shangri-La Dialogue.
He said that regardless of controversies over the Bush administration's security policies globally, "actually here in Asia the overall legacy is a pretty straightforward and very positive one."
Gates reiterated US pledges of continued engagement in Asian security. "I want to convey to you with confidence that any future US administration's Asia security policy is going to be grounded in the fact that the United States remains a nation with strong and enduing interests in this region – interests that will endure no matter which political party occupies the White House next," he said.