Donald Trump has questioned Kamala Harris' racial identity during a heated exchange at a convention for black journalists.

Trump falsely claimed the vice-president and presumptive Democratic nominee had not emphasised her Asian-American heritage until recently when, he claimed, "she became a black person".

"I didn't know she was black until a number of years ago when she happened to turn black and now she wants to be known as black," he said at the National Association of Black Journalists convention in Chicago on Wednesday.

"So I don't know - Is she Indian? Or is she black?"

Ms Harris said Trump's remarks were "the same old show" of "divisiveness... and disrespect".

"The American people deserve better," she told a meeting of the historically black sorority Sigma Gamma Rho in Houston. "We deserve a leader who understands that our differences do not divide us - they are an essential source of our strength."

Ms Harris is the first black and Asian-American vice-president, with Indian and Jamaican-born parents. She attended Howard University, a historically black university, and joined the predominantly black Alpha Kappa Alpha sorority.

She became a member of Congressional Black Caucus after entering the Senate in 2017.

Trump's claims prompted a heated exchange with ABC News' correspondent Rachel Scott, one of the moderators of the Chicago event.

"I respect either one," the Republican said in reference to Harris' racial identity. "But she obviously doesn't because she was Indian all the way and then all of a sudden she made a turn and she became a black person."

White House press secretary Karine Jean-Pierre said no-one "has any right to tell someone who they are, how they identify. That is no-one's right."

"Who appointed Donald Trump the arbiter of Blackness?" asked Representative Ritchie Torres of New York. He described Trump as a “relic of a racist past".

The Republican nominee and former president has a history of attacking his opponents on the basis of race.

He falsely accused Barack Obama, the country's first black president, of not being born in the US.

Trump attacked the former UN ambassador and his Republican primary opponent Nikki Haley by falsely claiming she could not be president because her parents were not US citizens when she was born.

Ms Harris has faced a series of attacks since becoming the presumptive Democratic nominee. Republicans have criticized the decision, saying she was chosen only because of her race.

Tim Burchett, a Republican congressman from Tennessee, called her a "DEI vice-president" - a reference to diversity, equity and inclusion programmes.

On Wednesday, Scott pushed Trump to clarify whether he believed Ms Harris was a "DEI hire". He replied: "I really don't know, could be."

Ms Harris has described growing up engaged with her Indian heritage and often visited the country. Her mother also immersed her two daughters in the black culture of Oakland, California - where she was raised, she said.

Trump also attacked Ms Harris' credentials during the discussion, saying she had failed her bar exam early in her legal career. His comments were met with murmurs from the crowd.

"I'm just giving you the facts. She didn't pass her bar exam and she didn't think she would pass it and she didn't think she was going to ever pass it and I don't know what happened. Maybe she passed it," he said.

Ms Harris graduated from the University of California Hastings College of Law in 1989. The New York Times reported that she failed her first attempt and passed at the second. The state bar of California says less than half of those who sit the test pass on the first attempt.

The Chicago discussion began with a contentious back and forth between Scott and the former president. Trump accused the journalist of giving a "very rude introduction" when she began the conversation asking about his past criticism of black people.

She cited Trump calling black journalists' questions ''stupid and racist'' and that he had ''dinner with a white supremacist at your Mar a Lago resort''.

"I love the black population of this country, I’ve done so much for the black population of this country,” he responded.

The former president criticised the conversation hours later on his social media platform. "The questions were rude and nasty, often in the form of a statement, but we CRUSHED IT!" he said.