New York: America, hit by the financial crisis, may lose its superpower status that has forced the country to dramatically scale down its engagement with the rest of the world, outgoing US Defence Secretary Robert Gates has said.

"I've spent my entire adult life with the United States as a superpower, and one that had no compunction about spending what it took to sustain that position," he said.

"It didn't have to look over its shoulder because our economy was so strong. This is a different time."

He said that it was the one of reasons behind his decision to step down.

"To tell you the truth, that's one of the many reasons it's time for me to retire, because frankly I can't imagine being part of a nation, part of a government … that's being forced to dramatically scale back our engagement with the rest of the world," he said.

Gates, who'll be succeeded by CIA chief Leon Panetta, served in both the Bush as well as Obama administration.

Gates said he had not been in favour of using ground troops to kill Osama bin Laden and preferred airstrikes.

"I was very explicit with the president in one of the discussions," Gates acknowledged.

"I said: 'Mr President, I want truth in lending. Because of experience, I may be too cautious, you know."

Gates also spoke about how he had reached out to Secretary of State Hillary Clinton.

"I just told her, based on my experience, that how well the administration worked would depend a lot on how well she and I got along together," Gates recalled.