Attorney General Jeff Sessions in the Roosevelt Room of the White House on Tuesday. (Jabin Botsford/The Washington Post)

The Justice Department is seeking to play a more muscular role in the Trump administration's immigration enforcement strategy, a move that is alarming immigrant rights advocates who fear Attorney General Jeff Sessions' hard-line ideology could give Justice too much clout in determining policy.

To highlight the department's expanding role, Sessions is considering making his first trip to the southern border in mid-April to Nogales, Ariz., a busy border crossing region that features a major patrol station and already has miles of fencing and walls designed to keep out illegal immigrants from Mexico. Aides emphasized that his itinerary is still being developed and the stop in Nogales — which would come as Sessions travels to a conference of state police officials from around the country 200 miles away in Litchfield Park — is still tentative.

If he follows through, the border visit would come at a time when President Trump is asking Congress for billions of dollars to begin construction on a longer and larger wall between the United States and Mexico, a central campaign promise.

In recent weeks, Sessions has taken steps to increase his department's focus on immigration.

He signed on to a letter released Friday with Homeland Security Secretary John F. Kelly backing the practice of arresting undocumented immigrants at courthouses, saying officials had to resort to such measures when states wouldn't cooperate on immigration enforcement.

President Donald Trump's White House Senior Adviser Stephen Miller listens during the daily press briefing at the White House on Monday. (Jabin Botsford/The Washington Post)

On Thursday, Sessions announced he is expanding a program to deport undocumented immigrants convicted of crimes after they serve their prison sentences, with the hope that the Justice Department can move more people straight from prison to their home countries rather than first moving them to immigrant detention facilities.

Justice said it would expand to 20 the number of prisons participating in the Institutional Hearing Program, which has immigration judges come directly to prisons or has the inmates participate in deportation hearings via video.

"We owe it to the American people to ensure that illegal aliens who have been convicted of crimes and are serving time in our federal prisons are expeditiously removed from our country as the law requires," Sessions said in a statement.

Earlier this month, Sessions used the release of a Federal Justice Statistics report on arrests and prosecution to highlight cases involving immigration offenses and he also issued a statement in support of an Immigration and Customs Enforcement report that listed cities that fail to comply with enforcement orders.

Last week, Sessions appeared in the White House briefing room to issue a threat to those cities that his agency could withhold federal law enforcement grants if they do not start to cooperate.

Sessions's activism has alarmed immigrant rights advocates concerned the department will play too powerful a role in a policy area that is typically the responsibility of the Department of Homeland Security.

"I think we want clarity over who's running immigration policy," Los Angeles Mayor Eric Garcetti said in an interview Thursday in Washington. Garcetti signed a directive two weeks ago prohibiting all city employees from using public resources to aide federal civil immigration actions.

"DOJ can give some opinions, but it's not primarily in their jurisdiction," Garcetti said. "So I know Senator Sessions has been very engaged, interested and involved in this area, but is he empowered by this administration beyond his formal responsibilities?"

Sessions, a former Republican senator from Alabama, was one of Congress's fiercest border hawks, and he helped scuttle former president Barack Obama's 2013 immigration reform effort on Capitol Hill that featured a path to citizenship for undocumented immigrants. One of his former Senate staffers, Stephen Miller, is Trump's senior policy adviser.

Kelly, a former Marine general with little experience in immigration issues, has also signaled that he will pursue a tougher stance on enforcement at DHS. He issued a pair of memos in February aimed at implementing Trump's executive orders to broaden the pool of undocumented immigrants prioritized for removal and beef up other border security measures.

But legal experts said Sessions could significantly restructure the Justice Department by ramping up the number of immigration judges sent to the border to speed up hearings and by pursuing more criminal prosecutions against immigrants in the United States beyond those associated with drug cartels and human smugglers that past administrations have focused on.

The Sessions Justice Department also could move to strip some protections from undocumented immigrants, such as how much time they have to find a lawyer; more robustly defend DHS enforcement policies that are challenged in court; and use the Office of the Special Counsel to aggressively prevent employers from discriminating against American workers by hiring undocumented workers, said Leon Fresco, a former deputy assistant attorney general in the Obama administration.

"I think they will be in­cred­ibly active," said Fresco, who helped draft the 2013 immigration bill while serving as an aide to Sen. Charles E. Schumer (D-N.Y.). The only thing that could slow Sessions, he added, was "finding enough individuals with expertise and the willingness to speed these issues along."

If Sessions follows through, it would represent a sharp break from the policies of his predecessors in the Obama administration. In 2010, the Justice Department, then led by Eric H. Holder Jr., sued Arizona over a state law that granted broad immigration enforcement powers to local law enforcement agencies. The Supreme Court in 2012 upheld a lower court's ban on key provisions in the law.

In January, Holder was hired by the California Legislature to represent the state in potential legal fights with the Trump White House.

"I believe there is nothing wrong, legally, morally or intellectually, with a lawful system of immigration that serves the national interest. What's wrong with that?" Sessions said in a speech to a conference of state attorneys general last month.

"People who come here unlawfully, who commit crimes, are going to be out of here," he added, punching a finger in the air for emphasis. "The law says that they have to be deported and we're going to insist that that happens."

Trump's budget proposal outlines how Sessions could turn his rhetoric into action.

It calls for the Justice Department to hire 75 more immigration judge teams to speed removal proceedings, along with 60 more border enforcement prosecutors and 40 more deputy U.S. marshals to apprehend and transport those in the country illegally.

The budget also calls for an additional $171 million to buy short-term detention space, much of which will likely be used to house undocumented immigrants.

"Immigration is one of their top priorities, permeating every part of their agenda, and every part of the federal government and agencies," Marielena Hincapié, executive director of the National Immigration Law Center, said of the Trump White House.

Sessions is "very much aligned with their ideology," she said. "He is very knowledgeable. He's worked on these issues for decades now and has very strong opinions. He's finally in a position of power to use the department toward his vision and use the attorney general role as a bully pulpit."

In Nogales, Sessions would tour a border region that was once viewed as the most porous section, leading authorities to build the border walls and fences. In 2013, a bipartisan group of senators, led by John McCain (R-Ariz.) and Schumer, visited the area during the immigration reform deliberations.

During the tour, McCain wrote on Twitter that they saw a woman scale the 18-foot bollard fence and drop down to the U.S. side of the border before she was apprehended by patrol agents. Some advocates suggested that the event was staged to support Republican calls for additional border security spending.

The Nogales barriers have had mixed results, officials said. Brandon Judd, president of the National Border Patrol Council, emphasized that any single-layered fencing is "defeatable."

Overall, Judd said, "we do not think a 2,000-mile wall, a great wall of the United States, is necessary. But we 100 percent support a wall in strategic locations that allow us to dictate the crossing points."