“She has years of experience. She is extremely intelligent,” Bernie Sanders allowed. | Getty Sanders tangles with Charlie Rose over Clinton's qualifications

Bernie Sanders is refusing to back down from his claim that Hillary Clinton is not "qualified" to be president, though he told CBS host Charlie Rose on Thursday that he only attacked her because she attacked him first.

“Do you believe Secretary Clinton is unqualified to be president?” Rose asked the Vermont senator on CBS Evening News on Thursday.


“Well, does Secretary Clinton believe that I am unqualified to be president?” Sanders shot back.

Rose pressed further, asking why Sanders would level such a charge against someone with "a first-class resume" and "one of the most qualified people to run."

“She has years of experience. She is extremely intelligent,” Sanders allowed.

“So why can't you say?” an exasperated Rose asked again.

“Because she is, you know, I have some experience, too,” Sanders said, launching into a recitation of his own years of public service.

But "you're right," he told Rose. "We should not get into this tit-for-tat. We should be debating the issues facing the American people. All I am saying is that if people are going to attack us, if they're going to distort our record as has been the case time and time again, we're going to respond.”

When asked about the campaign's shift in tone over the past week — away from issue-based contrasts toward personal attacks — Sanders admitted that he is embarrassed by the increasingly negative tenor of the primary. But he blamed Clinton and her allies for starting the fight.

"You said that Clinton should apologize for Iraq war deaths," Rose noted.

"This is after I was asked to apologize for the tragedy in Sandy Hook. You know, put these things in a context," Sanders responded defensively.

Ultimately, Sanders said that if Clinton is the Democratic nominee, he will back her.

"I think the idea of a Donald Trump or a Ted Cruz presidency would be an unmitigated disaster for this country," he said. "I will do everything in my power and work as hard as I can to make sure that that does not happen, and if Secretary Clinton is the nominee, I will certainly support her."