(CNN) - Former Defense Secretary Robert Gates is defending his criticism of Vice President Joe Biden's record on national security.
Gates writes in his new book, "Duty: Memoirs of a Secretary at War," that Biden was "wrong on nearly every major foreign policy and national security issue over the past four decades."
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He stood by his comments in an interview with Wolf Blitzer on CNN's "The Situation Room."
"I think I should have worked harder as secretary of defense to reach out privately to the Vice President to see if there wasn't a way to narrow our differences," Gates said on Thursday.
"The irony is that if you read the book, it's clear that I was in agreement with the Vice President on most of the issues facing the administration except for Afghanistan," he said.
For example, he and Biden were hesitant to support the 2011 U.S. special forces raid that ultimately killed al Qaeda leader Osama bin Laden and was supported by President Barack Obama.
Gates said that while he and Biden, a potential 2016 presidential candidate, agreed on this issue, their opposition was for different reasons.
"What I say in the book is that I think the Vice President was against the raid because of the domestic political consequences," he said.
"I was against the raid because successful or failure, I was worried that it would create such a problem with the Pakistanis they would shut down our line of communication in Afghanistan but at the very end I did turn around and support the raid."
Gates also writes that Obama lost faith in his own Afghanistan policy, which generated sharp controversy earlier in the week.
Gates weighed in on efforts in Congress to apply new sanctions on Iran as well as his biggest mistakes running the Pentagon for two presidents.
Gates agrees with Obama that imposing new sanctions on Iran now would probably "torpedo" a global effort aimed at getting Tehran to shelve its nuclear ambitions.
In addition to his wavering relationship with Biden, Gates said one of his biggest mistakes was "failing to get a chain of command problem fixed in Afghanistan quickly enough."
Gates, a Republican, was appointed secretary of defense by former President George W. Bush in 2006 and was asked to stay on by Obama. He left the position in 2011