In both cases, it was the right decision to fight and see the wars through, Rice, a southern-born black woman, said in an interview with Essence Magazine.
A major cause of the 1861-65 Civil War was the claim by states of the South that they had a right to allow slavery of black Africans.
Asked if she still thought the decision to go to war in Iraq in 2003 was right, considering the cost in lives and treasure, Rice said, "Absolutely."
Rice then offered a parallel between critics of the administration's Iraq policies and "people who thought it was a mistake to fight the Civil War to its end and to insist that the emancipation of slaves would hold."
"I'm sure that there were people who said, "Why don't we get out of this now, take a peace with the South, but leave the South with slaves?" she said.
"Just because things are difficult, it doesn't mean that they are wrong or that you turn back," Rice told the magazine, which has a large audience among African-Americans.
Rice, a former academic, said she spent the summer reading biographies of the Founding Fathers and she was certain "there were people who thought the Declaration of Independence was a mistake" as well.