BRIDGEWATER, N.J. (AP)

 Ahead of campaigning in Ohio yesterday, President Donald Trump unleashed a withering attack on the state's favourite son, savaging LeBron James in a late-night tweet that derided the intelligence of one of the nation's most prominent African-American men.

Trump blasted James after seemingly watching an interview the former Cleveland Cavaliers star did last week with CNN anchor Don Lemon in which he deemed Trump divisive.

Although James has long been a Trump critic, calling the president "U bum" in a 2017 tweet, last Friday night's tweet was Trump's first attack on the player, who just opened up a school for underprivileged children in his hometown of Akron.

"LeBron James was just interviewed by the dumbest man on television, Don Lemon," Trump posted. "He made LeBron look smart, which isn't easy to do."

Trump then, unexpectedly, appeared to weigh in on the growing debate over who is the greatest NBA player of all time, James or Michael Jordan, by writing "I like Mike!"

Trump, who spent Friday evening at a rally for a fellow Republican outside Columbus, has long denounced the media — CNN in particular — and rarely lets a slight go unnoticed.

But the attack on James, who was being interviewed by another black man, to some resembled a racial dog whistle and came just days after Trump deemed Democratic representative Maxine Waters of California, who is also black, as "low IQ" during a screed amid a rally in Pennsylvania.

Ohio Governor Josh Kasich, a Republican who at times criticises Trump, tweeted: "Rather than criticising @KingJames, we should be celebrating him for his charity work and efforts to help kids."

Trump has repeatedly been questioned about his views on race, from deeming many Mexican immigrants "rapists" during his campaign kick-off speech for the Republican presidential nomination to placing blame on "both sides" for the violent clash between white supremacists and counter protesters in Charlottesville, Virginia, a year ago.