President Trump and the North Korean leader, Kim Jong-un, “agree” in their negative assessment of former Vice President Joseph R. Biden Jr., the White House press secretary, Sarah Huckabee Sanders, said on Sunday.

Ms. Sanders, in an interview on NBC’s “Meet the Press,” also defended the president’s approach to efforts to denuclearize North Korea and deflected questions about whether Mr. Trump’s declaration of “treason” had predetermined the outcome of a review of the Russia investigation’s roots.

On Saturday, Mr. Trump seemed gratified that North Korea’s state media had described Mr. Biden, the Democratic candidate he views as the biggest threat to him in 2020, as a “fool of low IQ.”

“North Korea fired off some small weapons, which disturbed some of my people, and others, but not me,” Mr. Trump wrote as he was traveling in Japan. “I have confidence that Chairman Kim will keep his promise to me, & also smiled when he called Swampman Joe Biden a low IQ individual, & worse. Perhaps that’s sending me a signal?”