Trump traveled to the New York suburb to discuss efforts to combat the violent MS-13 gang, which he pledged to dismantle and deport.

"Together we're going to restore safety to our streets and peace to our communities and we're going to destroy the vile, criminal cartel MS-13 and many other gangs," Trump said.

Long Island has been particularly affected by the brutal street gang, with recent high-profile murders gripping the community there.

"We've gotten a lot of them out of here," Trump said, at times looking at his director of Immigration and Customs Enforcement. "But the rest are coming. They'll be out of here quickly, right? Quickly."

The speech was laced with violent imagery, with Trump saying MS-13 has rendered the suburb into "blood-stained killing fields."

"They kidnap. They extort. They rape and they rob," Trump said. "They stomp on their victims. They beat them with clubs, they slash them with machetes, and they stab them with knives. They have transformed peaceful parks and beautiful quiet neighborhoods into bloodstained killing fields. They're animals."

Trump repeatedly pledged in his speech, delivered in front of law enforcement officers at Suffolk County Community College, to have the backs of police and law enforcement.

"We're going to enforce our laws, protect our borders and support our police like our police have never been supported before," Trump said.

He praised the "rough" officers of ICE and suggested that police shouldn't protect the heads of suspects when they're arrested.

"When you see these thugs thrown into the back of a paddy wagon. You see them thrown in, rough. I said, 'Please don't be too nice,' " Trump said, mentioning observing the prisoner's heads being shielded. "I said, 'You can take the hand away.' "

The President also noted his longstanding campaign pledge to build a wall along the US border with Mexico.

"We're going to secure our border against illegal entry and we will build the wall, that I can tell you," Trump said, noting that the House on Thursday advanced $1.6 billion for the first wave of construction, though that still has to pass the Senate. "The wall is vital, and vital as a tool for ending the humanitarian disaster brought, and really brought on by drug smugglers and new words we haven't heard too much of, human traffickers."

Immigration agenda

Trump and his key surrogates -- Attorney General Jeff Sessions and Homeland Security Secretary John Kelly -- have spoken frequently about the perniciousness of MS-13 and its relationship to illegal immigration.

The gang has strongholds in the US, El Salvador, Guatemala and Honduras. The Obama administration's Treasury Department sanctioned the gang in 2012 as a transnational criminal organization -- the first such designation for a street gang. The US law enforcement community has also been fighting the gang for years.

"We will find you, we will arrest you, we will jail you and we will deport you," Trump said, painting with a broad brush to imply all the gang members are immigrants.

Sessions was in El Salvador this week to discuss the threat from that side of the border, as well, with the Justice Department announcing Thursday that Salvadoran prosecutors charged 113 MS-13 gang members.

While no expert disagrees that the gang is a particularly violent and brutal criminal organization -- whose preferred weapon is machetes -- there have been concerns about the Trump administration's use of the organization as a justification for its immigration policies.

Mara Salvatrucha, known as MS-13, actually began in the United States -- in Los Angeles in the 1980s amid a flood of Salvadorans fleeing a civil war to the US.

As the gang grew stronger, authorities also deported immigrants in the 1990s back to Central America, which is what first sent the gang to those countries, where it also took hold.

An administration official pointed to migration from Central America as the "principle factor" for MS-13's growth in the US, though the administration has been continuously unable to give reporters any hard numbers of how many suspected MS-13 members are immigrants or were gang members when they migrated to the US.

A Congressional Research Service analysis of MS-13 found that its ranks were continuously strengthened by deportees from the US returning home, even as members also migrated to the US.

A House homeland security subcommittee recently held field hearings in New York on the threat as it relates to unaccompanied minors coming illegally into the US, and witnesses repeatedly told lawmakers that undocumented immigrants and teenagers are especially vulnerable to becoming victims of the gang if communities don't do enough to support, welcome and protect those individuals.