Homeland Security Secretary Alejandro Mayorkas issued broad new directives to immigration officers Thursday saying that the fact that someone is an undocumented immigrant “should not alone be the basis” of a decision to detain and deport them from the United States.

The Biden administration will continue to prioritize the arrest and deportation of immigrants who pose a threat to national security and public safety and those who recently crossed a border illegally into the United States, Mayorkas said in an interview.

Mayorkas said Immigration and Customs Enforcement (ICE) officers should not attempt to arrest and deport farmworkers, the elderly and others who were vulnerable to deportation under the Trump administration, which allowed agents to arrest anyone in the United States illegally. He also said agents should avoid detaining immigrants who land on their radar because they spoke out against “unscrupulous” landlords or employers, or at public demonstrations. The new rules take effect Nov. 29.

“The overriding question is whether the noncitizen poses a current threat to public safety,” Mayorkas wrote in a memo to immigration and border agency heads Thursday.

“Are we going to spend the time apprehending and removing the farmworker who is breaking his or her back to pick fruit that we all put on our tables?” Mayorkas said in the interview. “Because if we pursue that individual, we will not be spending those same resources on somebody who does, in fact, threaten our safety. And that is what this is about.”

But the secretary also granted ICE agents far more discretion to decide whether to deport someone than officials did in the agency’s interim guidance Feb. 18, which required supervisors to sign off on some deportation cases to make sure agents followed the rules.

Mayorkas said he would monitor data showing agents’ compliance with the guidelines but would not micromanage them.

“I do trust the ICE workforce, and I do trust ICE leadership, and I do have confidence in my own leadership and the efforts that I have made engaging with the ICE workforce and discussing with them these very issues,” he said.

Mayorkas issued the new instructions to immigration agents at a critical juncture for the 11 million undocumented immigrants in the United States, most of whom have lived here for years, and for the controversial federal agency in charge of enforcing the immigration laws.

President Joe Biden has pledged to fight for a path to citizenship for them this year, but talks with Republicans have collapsed amid a new influx of migrants at the southwest border, and the Senate has hit back-to-back roadblocks in its effort to include a legalization process in the budget, with the Senate parliamentarian rejecting another proposal this week.

The left wing of the Democratic Party has called for officials to abolish ICE, saying it is secretive and difficult to monitor. Hundreds of state and local jurisdictions are so wary of the agency - saying they have sought to remove people who do not pose a threat, such as minivan-driving parents or relatives of people in the military - that they have limited their police and jails from working with them.

Republicans have slammed ICE for a dramatic drop in immigration arrests this year and filed lawsuits against the Biden administration, alleging that it has abdicated its responsibility to enforce federal immigration laws. Immigration arrests fell from 6,000 in December to 3,600 in August, according to ICE data.

Republican attorneys general in Texas and other states have filed lawsuits seeking to overturn the agency’s enforcement priorities and compel the Biden administration to fully enforce civil immigration laws. In August a federal judge in Texas blocked ICE’s Feb. 18 priorities, calling them “suffocating,” though an appeals court has since largely let them take effect as the lawsuit proceeds.

Mayorkas said he is seeking to redirect ICE’s public safety mission by training agents in the use of “prosecutorial discretion,” in which they weigh pros and cons in determining whether to detain and deport someone. He said he used similar tactics as a former U.S. attorney prosecuting crimes in Southern California, and said ICE’s workforce simply does not have the resources to deport all 11 million people.

ICE’s Feb. 18 guidelines provided more-specific directions to immigration agents to determine who to arrest and deport. The guidance effectively banned the deportation of immigrants unless they were violent and gang members or aggravated felons.

But Mayorkas said in the new memo that “whether a noncitizen poses a current threat to public safety is not to be determined according to bright lines or categories.”

“It instead requires an assessment of the individual and the totality of the facts and circumstances,” he wrote.

Typically a serious criminal would be a priority for arrest and deportation, he wrote.

But he added that cases can become “complicated.” He said agents should examine an array of factors, such as the seriousness of the offense, the sentence, whether they used a weapon and the length of their criminal history.

Agents would weigh that against mitigating factors that could allow them to stay in the country, such as if they arrived at a young age or have a mental condition, and if their deportation would affect their families in the United States.

Some people convicted of a crime but who do not pose a threat to public safety and have family in the United States could be allowed to stay, he said. Conversely, immigrants with no convictions but who are deemed dangerous might be detained and deported.

“We do not lessen our commitment to enforce immigration law to the best of our ability. This is how we use the resources we have in a way that accomplishes our enforcement mission most effectively and justly,” he wrote.

Advocates for immigrants have criticized the Biden administration for allowing detention levels to increase from approximately 15,000 people a day to nearly 24,000 people a day, after promising to limit detention. But Mayorkas said immigration arrests have changed. The vast majority of those in detention have recently crossed the southwest border and remain a priority for deportation under the new rules. He said the arrests of serious criminals has also risen.