Attorney General Jeff Sessions toured the U.S.-Mexico border Tuesday and unveiled what he described as a new get-tough approach to immigration prosecutions under President Donald Trump.

The nation's top law enforcement official outlined a series of changes that he said mark the start of a new era to rid American cities and the border of what he described as "filth" brought on by drug cartels and criminal organizations.

He announced the changes at a news conference following a morning tour of the border that included visiting a port of entry, where he exited an SUV in a white shirt and baseball cap before entering a restricted area. He later visited with Customs and Border Protection officers and agents.

Sessions credited Trump for a steep drop-off of border apprehensions this year and said the administration will bring more felony prosecutions against immigrants entering the country illegally.

"This is a new era. This is the Trump era," he said. "The lawlessness, the abdication of the duty to enforce our immigration laws, and the catch and release practices of old are over."

Sessions answered only a few questions from reporters following his remarks. He said all prosecutors would carefully protect the civil rights of people charged with crimes, and he defended Trump's proposed border wall, saying it will be another tool to fight illegal immigration amid efforts within the Justice Department and other branches of government to punish and deter border crossers.

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"The barrier, the wall, will have a great and positive impact and will continue our ability to follow through on a commitment to end the lawlessness," Sessions said.

Related: AG Sessions Threatens ‘Sanctuary Cities,’ Mayors Fight Back

Sessions has been expanding the Justice Department's role in the anti-immigration agenda of the Trump administration. But his speech Tuesday during his first visit to the border offered the most comprehensive look yet at his plans for federal prosecutions of those in the country illegally.

He directed the nation's federal prosecutors in a Tuesday memo to prioritize immigration-related cases, with an eye toward targeting people who cross the border illegally and those who come back after being deported.

Sessions urged federal prosecutors to intensify their focus on immigration crimes such as illegal crossing or smuggling others into the U.S., even though such prosecutions are already happening on a large scale. Half of federal arrests in 2014 were for immigration-related offenses, according to a Pew Research analysis released this week, based on the most recent federal statistics.

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Critics blasted the initiatives announced by Sessions as fear-mongering and anti-immigrant rhetoric not rooted in facts.

"Once again, Attorney General Sessions is scaring the public by linking immigrants to criminals despite studies showing that immigrants commit crimes at lower rates than the native born. He and President Trump are wasting more federal taxpayer dollars going after illegal border crossers instead of protecting the American public," said Gregory Z. Chen, director of government relations for the American Immigration Lawyers Association.

Sessions made the announcement in Nogales, a border city that has witnessed a dramatic drop in immigrant and drug smuggling in recent years as more people enter the country in Texas, many of them Central Americans fleeing violence in Guatemala, Honduras and El Salvador.

U.S. Attorney General Jeff Sessions, right, tours the U.S.-Mexico border on April 11 in Nogales, Arizona. Ross D. Franklin / AP

The Border Patrol's Tucson sector, which comprises most of Arizona, saw about 65,000 arrests of immigrants last fiscal year, roughly half the number agents made in 2012, according to Border Patrol data. Marijuana seizures have also dropped by about 28 percent from 1 million pounds in 2012 to 728,000 last year.

Following the border tour, Sessions was scheduled to deliver a keynote speech at an International Association of Chiefs of Police conference outside Phoenix. He'll also speak with service members at Luke Air Force Base near Phoenix.

Much of what Sessions outlined in his far-ranging speech is also addressed in the Justice Department's proposed budget. Even as it plans to cut the Justice Department's budget by more than $1 billion, the Trump administration wants hundreds of millions of dollars to hire 60 federal prosecutors and 40 deputy U.S. Marshals to focus on border cases.

It also wants to boost immigration courts by $80 million to pay for 75 additional teams of judges. That would speed up removal proceedings for people in the United States illegally and address a backlog of more than 540,000 pending cases. The proposal also calls for adding $1.5 billion to Immigration and Customs Enforcement's budget to find, detain and deport immigrants living in the U.S. illegally, along with more than $300 million to hire 500 new Border Patrol agents and 1,000 immigration agents.