Looming federal cuts to anti-terrorism funding totaling as much as $100 million would mean “New York City will become less safe,” Mayor Bill de Blasio said Wednesday.

Speaking to reporters gathered at an NYPD surveillance post in lower Manhattan, de Blasio and other local officials said they hoped to convince Congress to pass funding for a post-9/11 program that helps municipalities offset security costs.

Called the Urban Areas Security Initiative, the program awards grants of about $600 nationwide. The cuts would leave funding at about $330 million, according to the officials.

“If Congress doesn’t act, there’re going to be a lot of happy terrorists out there in the world, because they’re going to have a chance to come at us with less of our defenses up,” Bill de Blasio said.

De Blasio and the other elected officials want Congress to pass funding legislation to pay for the grants.

NYPD Commissioner William Bratton declined to say exactly what would be cut if the funding isn’t restored.

“We’ll cross that bridge when we come to it,” Bratton said.

U.S. Rep. Kathleen Rice (D-Garden City) called the possibility that anti-terror money might not pass “pathetic” — and noted that the threatened cuts would also impact other would-be targets.

“There are other cities across this country that need this funding as well, and we’ve seen terrorist attacks elsewhere,” Rice said, adding: “This is not just a New York City-centric thing.”

U.S. Rep Steve Israel (D-Dix Hills) warned that “the clock is ticking.”

The White House restored the money earlier this year after a public spat in which the President Barack Obama’s staff said that, of the $760 million homeland security grants given to the state and city over the past several years, about $620 million has not yet been spent.

Asked about the local officials’ Wednesday news conference, White House spokesman Peter Boogaard referenced comments on the issue from earlier this year by Obama press secretary Josh Earnest — presumably those from February, when Earnest criticized the “credibility” of U.S. Sen. Chuck Schumer, who demanded the cuts be restored.

Speaking Wednesday, de Blasio called the White House’s accounting claims “ridiculous.”

“Every dollar has been spent or is being spent,” de Blasio said.

Bratton then called the Obama administration’s position “smoke and mirrors” and blamed his budget office for being “very cute” in suggesting that New York was leaving money unspent.

“He started this whole mess,” Bratton said.