Mayor de Blasio and New Jersey Gov. Chris Christie are blasting Republican presidential candidate Donald Trump's call Monday for a "total and complete shutdown of Muslims entering the United States."
Trump's proposed ban would stand "until our country's representatives can figure out what is going on," according to a statement from Trump's campaign.
Trump said in the statement that his proposal comes in response to the level of hatred among "large segments of the Muslim population" toward Americans.
"Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by people that believe only in jihad, and have no sense of reason or respect for human life," Trump said in the statement.
De Blasio told reporters Monday afternoon the proposal is "against our American values. It's against everything this country is based on. It's as simple as that."
"This country was formed by people fleeing religious persection," he added. "When we founded this nation, it was to respect religious pluralism."
"How could the frontrunner for a major party nomination literally be suggesting a religious test on who gets to come into the country?" said de Blasio, clearly exasperated. "That is a dangerous, dangerous statement. That's why he must be confronted."
During an interview on CNN, he also ripped Trump's plan to list the nation's Muslims in a database, and said Trump's rhetoric was "dangerous" and "doing the bidding of our enemies."
Trump hit back on Twitter, saying de Blasio was "the worst mayor in the United States." Trump said he has watched New York, where he was a home, suffer from dirty streets, homelessness and crime.
He called the state of the city a "disgrace."
Meanwhile, New Jersey Gov. Chris Christie and competing Republican presidential candidate, responded on a radio show Monday: "This is the kind of thing that people say when they have no experience and don't know what they're talking about."
Christie said "the idea of banning Muslims from entering the country is just to me someone who's speaking from no experience."
Christie acknowledged the proposal is a clear violation of the First Amendment, "but there are folks in this race who don't care about what the law says."
"You do not need to be banning Muslims from the country," he said. "In my view, that's a ridiculous position and one that won't even be productive."
Christie said the government needs to be taking the opposite approach and embracing and cooperating with "peaceful Muslim Americans who want to give us intelligence against those who are radicalized."
"We did this after 9/11, and it was a very effective approach," he said. "I can tell you in New Jersey, we frequently had sources inside mosques that were giving us information that helped us to bring cases and intervene on things that we otherwise wouldn't have known about."
Trumps' comments quickly drew a response from the Council on American-Islamic Relations, whose communications director, Ibrahim Hooper, told NBC News: "Donald Trump sounds like a leader of a mob, not like a leader of a great nation like ours. He is doing the work of ISIS."
Trump campaign manager Corey Lewandowski said Trump's proposed ban would apply to "everybody," including Muslims seeking immigration visas as well as tourists seeking to enter the country.
He did not respond to questions about whether it would also include Muslims who are U.S. citizens and travel outside of the country, or how a determination of someone's religion might be made by customs and border officials.
In response to a request for additional detail, Trump said via a campaign spokeswoman: "Because I am so politically correct, I would never be the one to say. You figure it out!"
Trump's proposal comes a day after President Barack Obama spoke to the nation from the Oval Office in the wake of the shootings in San Bernardino, California, which Obama said was "an act of terrorism designed to kill innocent people."
The FBI said Monday the Muslim couple who carried out the massacre had been radicalized and had taken target practice at area gun ranges, in one case within days of the attack last week that killed 14 people.
Soon after Trump's announcement, U.S. Secretary of Homeland Security Jeh Johnson called on Americans not to vilify Muslims.
"Now more than ever it is time to work together, build bridges and pursue a stronger union," Johnson said at a press conference after a roundtable discussion with the All Dulles Area Muslim Society, which was already scheduled before Trump's comments.