NEW YORK (AP) — New York City Mayor and Democratic presidential candidate Bill de Blasio says President Donald Trump’s stated willingness to accept a foreign power’s help in his 2020 campaign should spur Congress to begin impeachment hearings.

De Blasio told MSNBC’s “Morning Joe” on Friday that Trump’s assertion in an ABC interview that he would not have to call the FBI if a foreign country offered information about an opponent was “openly treasonous”

De Blasio called the interview “the last straw” and said Congress should begin impeachment hearings. He said the nation can no longer accept “the notion of a president who openly invites interference in our election.”

The Democratic National Committee announced Thursday that de Blasio is among the 20 candidates who will appear in two nights of Democratic debates this month.