Story highlights Senator slams Trump after reports of heated phone calls with Australia and Mexico

"He's doing kind of amateur-hour stuff," ex-vice presidential nominee says

(CNN) Sen. Tim Kaine on Thursday called President Donald Trump's reportedly contentious phone calls with US allies Australia and Mexico "foolish."

"To have a contentious conversation and name-call a country or the Prime minister of a country that's one of our greatest allies in Asia is foolish," said the Democratic senator from Virginia, who was Hillary Clinton's running mate in 2016.

"To suggest to the President of Mexico we may have to send US troops into Mexico is foolish. Some of the statements that the President is making about Iraq and Iran are foolish."

Kaine added, "He's doing kind of amateur-hour stuff on matters of significant national importance."