Joe Biden declared he "should not have been so cavalier" on Friday after he told a prominent black radio host that African-Americans who back President Donald Trump "ain't black".
The presumptive Democratic presidential nominee quickly moved to address the fallout from his remark, which was interpreted by some as presuming that black Americans would vote for him.
In a call with the US Black Chamber of Commerce, Mr Biden said he would never "take the African-American community for granted".
"I shouldn't have been such a wise guy," Mr Biden said. "No one should have to vote for any party based on their race or religion or background."
That was an acknowledgement of the stinging criticism he received in response to his comments, which he made earlier in the day on The Breakfast Club, a radio program that is popular in the black community.
The rebukes included allies of Mr Trump's re-election campaign and some activists who warned that Mr Biden must still court black voters, even if African-Americans overwhelmingly oppose the president.
"None of us can afford for the party or for this campaign to mess this election up, and comments like these are the kinds that frankly either make black voters feel like we're not really valued and people don't care if we show up or not," said Alicia Garza, a Black Lives Matter co-founder and principal of Black Futures Lab.
Near the end of Mr Biden's appearance on the radio program, host Charlamagne Tha God pressed him on reports that he is considering Minnesota Senator Amy Klobuchar, who is white, to be his vice presidential running mate. The host told Mr Biden that black voters "saved your political life in the primaries" and "have things they want from you".
Mr Biden said: "I guarantee you there are multiple black women being considered. Multiple."
A Biden aide then sought to end the interview, prompting the host to say, "You can't do that to black media".
Mr Biden responded, "I do that to black media and white media," and said his wife needed to use the television studio.
He then added: "If you've got a problem figuring out whether you're for me or for Trump, then you ain't black."
Mr Trump's campaign and his allies immediately seized on Mr Biden's comments. South Carolina Senator Tim Scott, a Trump supporter and the Senate's sole black Republican, said he was "shocked and surprised" by Mr Biden's remarks.
"I was struck by the condescension and the arrogance in his comments," Mr Scott said in a conference call arranged by the Trump campaign. "I could not believe my ears that he would stoop so low to tell folks what they should do, how they should think and what it means to be black."
Black voters helped resurrect Mr Biden's campaign in this year's primaries with a second-place finish in the Nevada caucuses and a resounding win in the South Carolina primary after he had started with embarrassing finishes in overwhelmingly white Iowa and New Hampshire. Sixty-one percent of black voters supported Mr Biden during the primary season, according to AP VoteCast surveys across 17 states that voted in February and March.
Mr Biden is now seeking to maintain his standing with black voters while building the type of multiracial and multigenerational coalition that twice elected Barack Obama, whom he served as vice president. He has already committed to picking a woman as his running mate and is considering several African-American contenders who could energise black voters. But Mr Biden is also considering candidates such as Klobuchar, who could appeal to white moderates.
There is little chance of a sudden shift in support for Trump among black voters. A recent Fox News poll shows just 14 per cent of African-Americans who are registered to vote have a favorable opinion of Trump, compared with 84 per cent who view him unfavorably.
Seventy-five per cent of African-American registered voters say they have a favourable view of Mr Biden; 21 per cent hold an unfavourable opinion.
Mr Biden's selection of a running mate, along with his pledge to appoint the first black female Supreme Court justice, could help motivate voters. Several black women are among those under consideration, including California Senator Kamala Harris, Georgia voting rights advocate Stacey Abrams, Atlanta Mayor Keisha Lance Bottoms, Florida Representative Val Demings, Ohio Representative Marcia Fudge and Susan Rice, Obama's former US ambassador to the UN.