(Advisory: This story contains language that some may find offensive in paragraph 17)

WASHINGTON (Reuters) - Former Vice President Joe Biden came under sharp criticism from some of his Democratic presidential rivals on Wednesday for remarks he made this week about his time working civilly with segregationists serving in the Senate in the 1970s.

U.S. Senator Cory Booker, who is also seeking the Democratic nomination, called on Biden to apologize.

“Frankly, I’m disappointed that he hasn’t issued an immediate apology for the pain his words are dredging up for many Americans. He should,” Booker, who is black, said in a statement.

The criticism exposed bubbling racial and generational tensions within the Democratic field that is the most diverse in history. Biden, 76, is leading in early opinion polls in the crowded Democratic contest to take on Republican President Donald Trump in the November 2020 election.

Speaking to reporters on Wednesday evening, Biden was asked about Booker’s demand that he apologize. “Apologize for what? Cory should apologize. He knows better. Not a racist bone in my body. I’ve been involved in civil rights my whole career,” Biden said.

At a fundraiser in Potomac, Maryland, a suburb of Washington, Biden cited civil rights leader the Rev. Martin Luther King Jr. as a personal “hero” and an inspiration for his political career.

Biden’s campaign said he was not endorsing the positions of the segregationists he named but using them as an example of someone with whom he disagreed.

“And I think anyone who served with Joe Biden, you know, whether it was in the Senate or whether they worked with him during his eight years as Barack Obama’s vice president, knows that this is a man who is committed to equality and civil rights in this country,” Anita Dunn, a senior Biden aide, told MSNBC.

‘WE GOT THINGS DONE’

At issue are Biden’s remarks at a New York fundraiser for his presidential campaign on Tuesday night.

FILE PHOTO: New York City Mayor and Democratic Presidential candidate Bill de Blasio leaves a rally against new restrictions on abortion passed by legislatures in eight states including Alabama and Georgia, in New York City, U.S., May 21, 2019. REUTERS/Jeenah Moon/File Photo

Biden said U.S. leaders had lost the ability to work together. He pointed to two segregationists from the South who were serving in the Senate when he was first elected - Democratic Senators James Eastland of Mississippi and Herman Talmadge of Georgia.

Eastland described black people as inferior and fought against efforts to desegregate the South. When Biden joined the U.S. Senate in 1973, he and fellow Democrat Eastland served on the same committee.

“At least there was some civility. We got things done. We didn’t agree on much of anything. We got things done. We got it finished,” Biden said, according to a pool report distributed by his campaign. “But today, you look at the other side and you’re the enemy. Not the opposition, the enemy. We don’t talk to each other anymore.”

New York Mayor Bill de Blasio, who is also seeking the Democratic nomination, criticized Biden’s remarks.

“It’s past time for apologies or evolution from @JoeBiden,” de Blasio wrote on Twitter. “He repeatedly demonstrates that he is out of step with the values of the modern Democratic Party.”

De Blasio called out Biden for invoking Eastland, posting a photo of himself on Twitter with his wife, who is black, and his two multiracial children.

“It’s 2019 & @JoeBiden is longing for the good old days of ‘civility’ typified by James Eastland. Eastland thought my multiracial family should be illegal & that whites were entitled to ‘the pursuit of dead n*ggers,’” de Blasio wrote on Twitter.

Booker also criticized Biden for his use of the word “boy” - a term that was frequently used by racists to demean black men.

While describing Eastland, Biden said: “He never called me boy, he always called me son.”

Booker said it was inappropriate to “joke about calling black men boys.”

“Vice President Biden’s relationships with proud segregationists are not the model for how we make America a safer and more inclusive place for black people, and for everyone,” Booker said.

Another Democratic candidate, former congressman John Delaney, offered a more restrained criticism.

“Evoking an avowed segregationist is not the best way to make the point that we need to work together and is insensitive. We need to learn from history, but we also need to be aggressive in dismantling structural racism that exists today,” Delaney said in a statement.