John Kerry, the former secretary of state and potential 2020 hopeful, called on President Trump to step down during a Tuesday appearance at the World Economic Forum in Davos, Switzerland.

Kerry, who lost his bid for the presidency in 2004, made the statement during a panel in which he was asked a hypothetical question: What his message for Trump would be if he were sitting next to him?

"He doesn’t take any of this seriously,” said the former U.S. senator.

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When pressed by CNBC's Tania Bryer, Kerry gave a one-word response: "Resign."

Trump was scheduled to travel to Davos for the summit but canceled due to the ongoing partial government shutdown. The president ridiculed the media early Tuesday in a Twitter post acknowledging this year’s absence.

"Last time I went to Davos, the Fake News said I should not go there" he tweeted. "This year, because of the Shutdown, I decided not to go, and the Fake News said I should be there."

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Kerry has been a consistent Trump critic. After the September release of Bob Woodard’s book “Fear,” which claimed to provide inside knowledge of the Trump White House, Kerry said the alleged details scare him.

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Following the resignation of former Secretary of Defense Jim Mattis earlier this year, Kerry slammed Trump’s "pull-out, walk-away presidency" and described Trump’s decision to pull out U.S. troops from Syria a "moment of shame."

When the former Democratic presidential nominee was asked if he would consider running again in 2020, Kerry said he hasn't "taken anything off the table."