DES MOINES, Iowa (AP) — The White House says Joe Biden's plan to call President Donald Trump an "existential threat" to the nation is "truly laughable" as the two politicians converge in Iowa on Tuesday.

White House press secretary Sarah Sanders says she's not sure whether Trump will respond to the former vice president, whose prepared remarks criticizing Trump were released ahead of his Iowa speech.

Sanders says, "The idea that he would say that the president poses any type of threat is truly laughable considering he was part of the administration that allowed Russia to interfere in our election."

Sanders says Biden was a key member of an Obama administration that also allowed China to grow and North Korea to test missiles. She says Biden has "got a lot of explaining to do."

Biden plans to use his Iowa visit to criticize Trump's economic policy.