"I think in that same interview, he praised what he called the 'revolution of values' in Cuba, and talked about how people were working for the common good, not for themselves," Clinton said at the Democratic debate audience in Miami.

ADVERTISEMENT

"I just couldn't disagree more," the former secretary of State added.

"You know, if the values are that you oppress people, you disappear, you imprison people, even kill people, for expressing their opinions ... that is not the kind of revolution of values that I ever want to see anywhere."

Clinton's remarks followed the debate moderators screening a 1985 video – first reported by Buzzfeed – of Sanders praising Castro.

"Everybody was totally convinced that Castro was the worst guy in the world," Sanders says in the archival video. "All the Cuban people were going to rise up in rebellion against Fidel Castro. They forgot that he educated their kids, gave them healthcare, totally transformed the society."

The moderator gave Sanders an opportunity to disavow his past praise for Castro, but the Vermont senator declined to do so.

"What that was about was saying that the United States was wrong to try to invade Cuba, that the United States was wrong to try to support people to overthrow the Nicaraguan government," Sanders said.

Asked whether he regretted praising Castro, Sanders, a self-termed democratic socialist, avoided the question and reiterated that the key question was whether or not the United States should be pushing for regime change in foreign countries.

"Cuba is, of course, an authoritarian, undemocratic country and I hope very much, as soon as possible, it becomes a democratic country," Sanders said.

"But on the other hand it would be wrong not to state that in Cuba they have made some good advances in healthcare, they are sending doctors all over the world.

"They have made some progress in education."