Former Mayor Bill de Blasio said New York City must be on alert to thwart Terrorism in the Big Apple following Hamas’ surprise invasion of Israel. 

“Of course we stand with the people of Israel,” de Blasio said Sunday on WABC 770 AM’s “The Cats Roundtable” with host John Catsimatidis Sunday.

“We’ve got to condemn [terrorism] wholeheartedly the second you see it. New Yorkers have felt terrorism. We know exactly what terrorism is, in ways that a lot of other people have not experienced,” the former mayor said, alluding to the Sept. 11, 2001 terror attacks.

He said Hamas’ slaughter of innocent Israelis shows that terrorism has not gone away.

“For New York City right now, we’ve got to be ready … Let’s be honest. This threat is going to exist in the world for quite a while, and we’ve got to protect ourselves,” said de Blasio.

He said under his leadership, the NYPD beefed up its anti-terror capabilities and said the department is prepared to protect New Yorkers.

Mayor Eric Adams, de Blasio’s successor, also slammed Hamas’ terror campaign and defended Israel.

De Blasio, a longtime supporter of Israel who teaches at NYU and formerly taught at Harvard, also ripped fellow progressives on the left — particularly in academia — for callously cheering on Hamas’ massive killing of innocent Jews in Israel, or failing to condemn it.

He said such an inhumane response undermines the Palestinian cause for statehood.

He called the Hamas’ terror attacks in Israel “disgusting and inhumane.” 

“There can’t be any moral relativism or mincing words here. What we saw was disgusting and unacceptable and needs to be condemned by everyone across the spectrum,” de Blasio said.

“I’m teaching at NYU. We had an unfortunate situation where the student leader was trying to justify the terrorism of Hamas. Luckily, a lot of us in the NYU community spoke out against that very quickly. I think that’s what people have to do.”

He said Harvard campus has been slow-footed in condemning the Hamas’ terror.

Follow along with The Post’s live blog for the latest on Hamas’ attack on Israel

He said people who say they care about Palestinians should “start by condemning Hamas and what they’ve done … I think some of the groups at Harvard haven’t done that — because I still have a connection there.”

 He said he signed onto a letter distributed by some Harvard groups condemning the Hamas’ terrorism.

“We don’t accept this. We don’t accept any form of terrorism. And we don’t accept the environment of a campus that includes organizations that somehow don’t think it’s necessary to see us all as human beings. That if Jewish lives have been destroyed, and children killed in front of their families, that somehow that doesn’t need to be spoken to. Of course, that has to be condemned,” the former two-term mayor said.

He said he believes in a two-state solution for Israel and Palestinians.

“I think you’ve got to protect democracy and Israel. That’s part of what makes Israel so strong. You can have those political differences and still say, ‘Let’s defend the state of Israel no matter what, because of what it means in the world. It’s the only refuge that the Jewish people have,’” de Blasio said.