North Korea's state-run news agency issued a blistering attack last week on Biden, who has been critical of the reclusive communist state in the past.

"I think they agree in their assessment of former vice president Joe Biden," Sanders said of Trump and Kim. She was speaking from Japan during a ceremonial visit by Trump.

"The president doesn't need somebody else to give him an assessment of Joe Biden. He's given his own assessment a number of times."

Trump, a Republican, referenced the criticism in a Twitter post on Saturday in which he mentioned Biden, a Democrat who is running for president, initially misspelling his name as Bidan and taking pleasure in the North Korean leader's sharp rhetoric about a fellow American.

Trump said in a subsequent corrected tweet that he smiled when Kim "called Swampman Joe Biden a low IQ individual, & worse. Perhaps that's sending me a signal?"

Trump on Sunday dismissed concerns about recent missile launches from North Korea and said he was confident that Kim would keep promises that he had made.

Australian Associated Press