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Story highlights

Clinton characterized Sanders as an unrealistic over-promiser in her book

She said that his attacks against her during the primary caused "lasting damage"

(CNN) —  

Vermont Independent Sen. Bernie Sanders on Wednesday shrugged off criticism made by his former presidential primary challenger Hillary Clinton in her new book about the 2016 election, saying that he’s instead focused on new issues.

“My response is that right now it’s appropriate to look forward and not backward,” he said in a statement. “I’m working overtime now to see we overturn (President Donald) Trump’s decision on (the Deferred Action for Childhood Arrivals program), pass a $15-an-hour minimum wage and next week I’ll be offering a Medicare-for-all single-payer system.”

“Our job is to go forward,” he added.

His comments refer to passages in Clinton’s new book, “What Happened,” which lobbed some heavy criticism at her former Democratic challenger. CNN obtained a copy of the book earlier this week.

In it, Clinton characterized Sanders as an unrealistic over-promiser.

She said that his attacks against her during the primary caused “lasting damage” and paved the way for “(Donald) Trump’s ‘Crooked Hillary’ campaign.”

Clinton wrote that Sanders “had to resort to innuendo and impugning my character” because the two Democrats “agreed on so much.”

Clinton also noted in the book that the Vermont independent “isn’t a Democrat.”

“That’s not a smear, that’s what he says,” she wrote. “He didn’t get into the race to make sure a Democrat won the White House, he got in to disrupt the Democratic Party.”

She added: “I am proud to be a Democrat and I wish Bernie were, too.”

The excerpts represent a small number of the roughly 500-page book in which Clinton reflects on her stunning loss to Donald Trump in 2016. The few pages on Sanders are also remarkably candid for a candidate who was more known for being careful than blunt, especially when it came to the Vermont senator.

The book is set for widespread release next week.

CNN’s Dan Merica contributed to this report.