US Republican presidential candidate Donald Trump opened a new tab questioning whether his Democratic rival Kamala Harris is "Black" during a contentious interview at the country's largest annual gathering of Black journalists on Wednesday.

"Is she Indian or is she Black?" Trump said of his opponent in the presidential race, drawing a smattering of jeers from an audience of about 1,000 people. "She was Indian all the way, and all of a sudden she made a turn and became a Black person."

Harris, who is of Indian and Jamaican heritage, has long self-identified as both Black and Asian. She is the first Black and Asian American to serve as US vice president.

"What he just said is repulsive," White House Press Secretary Karine Jean-Pierre said at a briefing in response to Trump's remarks. "It's insulting."

Since launching her White House campaign earlier this month, Harris has faced a barrage of sexist and racist attacks online, with some far-right accounts questioning her racial identity. Republican Party leaders have urged lawmakers to refrain from personal attacks and focus on her policy positions.

Trump himself has used personal insults against Harris and said he was going to ignore advice that he tone down his rhetoric in this campaign. "I'm not gonna be nice!" he told supporters at one campaign rally.

Trump also declined to say on Wednesday whether Harris was a "DEI hire," as some Republicans have claimed, saying, "I don't know."

DEI stands for "diversity, equity and inclusion" initiatives aimed at increasing the representation of women and people of colour in the workforce to address longstanding inequities and discrimination. The term "DEI hire" is now used to suggest a person is not qualified and was chosen based on race or gender.

The panel interview at the National Association of Black Journalists' annual convention in Chicago started on a tense note when ABC News reporter Rachel Scott listed a series of racist comments Trump had made and asked why Black voters should support him.

In response, Trump called the question "horrible," "hostile" and a "disgrace" and described ABC as a "fake" network.

"I have been the best president for the Black population since Abraham Lincoln," he boasted.

Trump repeated a line from the presidential debate in June, claiming that migrants crossing the U.S. southern border would take away "Black jobs," a term that drew criticism from some Black leaders.

"What exactly is a 'Black job,' sir?" Scott asked him.

"A Black job is anybody with a job," Trump replied.

When asked about his position on granting police officers immunity following the death of Sonya Massey, a Black woman who was shot and killed by a sheriff's deputy in Illinois, Trump acknowledged that he didn't know much about the case - drawing some gasps from the crowd - but added that "it didn't look good to me."

The interview began more than an hour late, which the Trump campaign said was due to problems with the event's audio equipment. An NABJ spokesperson did not immediately comment on what caused the delay. The session, originally scheduled for an hour, ended abruptly after 30 minutes when the campaign said he was out of time, according to Scott.

Trump's invitation had received a backlash from some members, prompting a co-chair of the convention to step down in protest. During the interview, some of Trump's false statements were met with murmurs and laughter from the crowd.

At one point, someone yelled out, "Sir, have you no shame?" before others shushed him.

Leah Mallory, a 21-year-old at Fordham University, described the conversation as "unreal."

"I honestly feel like it wasn't as conducive as we hoped it would be," she said. "I feel like what we heard were several things that he said before, and there were questions that weren't fully answered."

Courting Black voters

Trump has been actively courting Black voters and has held events in cities with large Black populations, including Atlanta, where he plans a rally on Saturday.

He had made inroads with Black men in particular after President Joe Biden, his former Democratic opponent, struggled to mobilize Black voters, traditionally the most loyal Democratic voting bloc. Biden won Black voters 92%-8% over Trump in 2020, according to Pew Research.

However, Biden's decision to step down in favour of Harris could make it more challenging for Trump to maintain his gains.

The presidential race is likely to come down to narrow margins in a handful of battleground states. A national Reuters/Ipsos poll released on Tuesday showed Trump leading Harris by 43%-42%, within the poll's margin of error.

The Black Journalists' Association, founded in 1975, regularly invites presidential candidates to address its annual gathering, but Trump was the first Republican to accept the offer since George W. Bush in 2004.

The association's president, Ken Lemon, said in a statement, "While we acknowledge the concerns expressed by our members, we believe it is important for us to provide our members with the opportunity to hear directly from candidates and hold them accountable."

Trump frequently goes after the media on the campaign trail, calling news outlets the "fake news," and sparred often with members of the White House press corps during his 2017-2021 presidency.

Harris, who did not attend the convention, is scheduled to speak to a Black sorority in Houston later on Wednesday.