When asked about Biden, Gates also said he would also do well in the role.
"I suppose to be even-handed I would have to say I suppose he would," he said.
Gates, who in his book said Biden was "wrong on nearly every major foreign policy and national security issue over the past four decades," conceded that he sometimes agreed with the Vice President. And Gates had additional praise for Clinton.
"The thing that I like best about Secretary Clinton, other than the fact that she has a great sense of humor, was she's very tough-minded," he said.