Democratic presidential candidate Kamala Harris confronted front-runner Joe Biden on race during a debate on Thursday, saying Biden's remarks about working with pro-segregationist senators were "hurtful" and questioning his 1970s opposition to school busing.

Harris, the daughter of Jamaican and Indian immigrants, said the issue of race was deeply personal for her and looked straight at Biden to challenge him to explain himself.

"I do not believe you are a racist. And I agree with you when you commit yourself to the importance of finding common ground," said Harris, 54, a U.S. senator from California.

"But I also believe - and it's personal and it was hurtful to hear you talk about the reputations of two United States senators who built their reputations and career on the segregation of race in this country."