US Democratic presidential nominee Joe Biden said he regrets his remarks that if African-American voters back President Donald Trump’s re-election, then they “ain’t black”.

“Well I tell you what, if you have a problem figuring out whether you’re for me or Trump, then you ain’t black,” Biden said earlier on Friday in a popular radio show.

Throughout the 18-minute interview, Biden stressed his longstanding ties to the black community, noting his overwhelming win this year in South Carolina’s presidential primary, a state where the Democratic electorate is more than 60 per cent African-American, the BBC reported.

“I won every single county. I won the largest share of the black vote that anybody had, including Barack,” he said of former President Barack Obama, the country’s first African-American president, who picked Biden as his running mate.

The remarks sparked sharp criticism from Republicans and some Democrats who accused him of lecturing black people on how to think and of questioning the racial authenticity of African-American voters.

Later on Friday, Biden described his comment as “cavalier” and said he never meant to seem as if he was taking black voters for granted or telling them who they ought to support.

“I should not have been so cavalier… I’ve never, never, ever taken the African American community for granted,” the BBC quoted Biden as saying.

“I shouldn’t have been such a wise guy. No-one should have to vote for any party based on their race, their religion, their background,” he added.

Biden campaign adviser Symone Sanders defended the comments on Friday, saying they were made “in jest”.

“Let’s be clear about what the VP was saying: he was making the distinction that he would put his record with the African American community up against Trump’s any day. Period.”

But Patrick Gaspard, a former top aide in the former Barack Obama administration, was quoted by a The Hill report as saying that Biden “is in no position” to “determine who is black enough or not”.

“White liberal elitists have continuously dictated which black Americans are allowed to come to the table and have a voice,” said Katrina Pierson, a senior adviser to the Trump campaign and leader of its Black Voices for Trump group.

Her comment was echoed by Senator Tim Scott, a black Republican, saying: That is the most arrogant, condescending comment I’ve heard in a very long time.”

Keith Boykin, a former aide to Democratic President Bill Clinton, tweeted: “Yes, Biden is a much better choice for black people than racist Trump. But white people don’t get to tell black people what is black. Biden still has to earn our vote.”

Derrick Johnson, president of the National Association for the Advancement of Colored People (NAACP), told CBS News that Biden could not “take the African-American vote for granted”.