President Trump's tweeted comments about Puerto Rico, and specifically San Juan Mayor Carmen Yulin Cruz, are "unspeakable," Sen. Bernie Sanders (I-Vt.) told host Jake Tapper in an appearance on CNN's State of the Union Sunday.

"It is unspeakable, and I don't know what world Trump is living in," Sanders said. "People in Puerto Rico are suffering one of the worst disasters in the history of that island. We have got to do everything we can to help them. We all have got to remember the people of Puerto Rico are American citizens, entitled to the same help as the people of any other community in America."

Trump's public response to Puerto Rico's devastation by Hurricane Maria struck many critics as too little, too late, and since focusing on the island territory, the president has turned much of his attention to labeling Cruz "nasty," a "poor" leader, and, by implication, a "politically motivated ingrate."