US attorney general says mail-in voting open to 'fraud and coercion'

US Attorney General William Barr said on Wednesday that mail-in ballots for the November 3 election could be vulnerable to fraud, echoing an argument President Donald Trump has made to denounce the use of voting by mail.

"As a matter of logic it's very open to fraud and coercion. It's reckless and dangerous, and people are playing with fire," Barr said in an interview with CNN.

Experts say voter fraud of any kind is exceedingly rare in the United States.