Democratic presidential candidates harshly criticized President Donald Trump’s remarks that he wouldn’t necessarily call the FBI if offered information from a foreign government about them.

“President Trump is once again welcoming foreign interference in our elections,” tweeted former Vice President Joe Biden. “This isn’t about politics. It is a threat to our national security. An American President should not seek their aid and abet those who seek to undermine democracy.”

In an interview with ABC News, Trump said he would listen to what they had to say and might not call the FBI.

“I think you might want to listen,” Trump said. “There’s nothing wrong with listening. If somebody called from a country [such as] Norway, [saying] we have information on your opponent. Oh, I think I’d want to hear it. It’s not an interference. They have information. I think I’d take it.”

Massachusetts Sen. Elizabeth Warren, who called for Trump to be impeached after Special Counsel Robert Mueller’s report became public, again called for his impeachment, as did former Texas Rep. Beto O’Rourke. Vermont Sen. Bernie Sanders and New York Sen. Kirsten Gellibrand called for the House to begin impeachment hearings.

California Sen. Kamala Harris called Trump a “national security threat,” New Jersey Sen. Cory Booker said the comments were “disgraceful” and Trump “unfit for the office you hold,” and Minnesota Sen. Amy Klobuchar said “the 2020 elections are not secure.”

Washington Gov. Jay Inslee called the remarks “dangerous and un-American,” Ohio Rep. Tim Ryan called them “shameful,” former HUD Secretary Julían Castro said Trump “is now essentially calling for open season on our elections,” and Colorado Sen. Michael Bennet said he is “threatening the integrity of our democracy.”

Contact us at letters@time.com.