NEW YORK (CBSNewYork/AP) — Mayor Bill de Blasio has denounced President Donald Trump’s executive action suspending the nation’s refugee program and temporarily banning those coming from countries with terrorism concerns.

“President Trump’s executive order is simply un-American,” de Blasio tweeted Sunday morning.

De Blasio went on to say that one of the reasons why New York City is so safe is because the New York City Police Department works closely with immigrant communities.

“If undocumented Americans feel like they can’t talk to the police about a crime they witnessed, that makes us less safe,” de Blasio said.

“President Trump’s executive order erodes our Constitutional rights,” de Blasio added. “If this is where he’s starting, imagine where he’s going.”

Earlier this week, de Blasio and other city leaders expressed their opposition of Trump‘s plans to cut off millions of dollars in federal funding to sanctuary cities.

De Blasio said the loss of funds would cut the resources of the NYPD — including anti-terrorism funding — and damage relations between police officers and communities. He added that the city would not begin deporting law-abiding undocumented immigrants because of the order.

U.S. Sen. Charles Schumer (D-N.Y.) also appeared alongside refugees and their families to denounce the ban at a press conference in New York City late Sunday morning:

“Donald Trump seems to want us to believe that immigrants are terrorists and criminals but look at these families, they are the promise of America,” Schumer said.

Schumer also praised Republican lawmakers that spoke out against the ban, and urged for bipartisan support to reach a resolution.

“Maybe we can pass something in the Congress but we can only do it with Republican support,” Schumer said.

Among those expressing opposition was Sen. Rob Portman, R-Ohio, who said Sunday that it would be best for the new president to “slow down” and work with lawmakers on how best to tighten screening for foreigners who enter the United States.

Portman said everyone should “take a deep breath and come up with something that makes sense for our national security” and reflects the fact that “America’s always been a welcoming home for refugees and immigrants.” He said America is “this beacon of hope and opportunity for the rest of the world” and should remain that way.

Senate Majority Leader Mitch McConnell, R-Ky., said he supports more stringent screening mechanisms, but cautioned that Muslims are some of the country’s “best sources in the war against terror.”

“I think it’s a good idea to tighten the vetting process But I also think it’s important to remember that some of our best sources in the war against radical Islamic terrorism are Muslims, both in this country and overseas,” he said.

He stressed the need “to be careful as we do this,” and said it would be up to the courts to decide “whether or not this has gone too far.”

President Donald Trump signed the executive action Friday night. The order imposes a 120-day suspension of the entire U.S. Refugee Admissions Program and a 90-day ban on all entry to the United States from countries with terrorism concerns.

EXTRA: Click Here To Read Full Stay Order

The State Department said the three-month ban in the directive applies to Iraq, Syria, Iran, Sudan, Libya, Somalia and Yemen — all Muslim majority nations.

On Saturday, U.S. District Judge Ann Donnelly issued a temporary stay the after lawyers for the American Civil Liberties Union filed a court petition on behalf of people who were detained at airports across the as the ban took effect.

The detainment of hundreds of travelers sparked protests across the country Saturday night and into Sunday morning, including protests at John F. Kennedy International Airport in Queens.

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