Agents also have been told to review government files to identify any jailed immigrants they might be able to release under the program.

The directives from the Homeland Security Department mark an unusual change for U.S. immigration enforcement, placing the obligation on the government for identifying immigrants who might qualify for lenient treatment. Previously, it was the responsibility of immigrants or their lawyers to assert that they might qualify under rules that could keep them out of jail and inside the United States.

It's akin to the Internal Revenue Service calling taxpayers to recommend they should have used certain exemptions or deductions.

The training materials apply to agents for Customs and Border Protection and Immigration and Customs Enforcement. They instruct agents "to immediately begin identifying persons in their custody, as well as newly encountered persons" who may be eligible for protection from deportation.

One training document includes scenarios describing encounters between agents and immigrants with guidance about how agents should proceed, with a checklist of questions to determine whether immigrants might qualify under the president's plans. ICE officials earlier began releasing immigrants who qualified for leniency from federal immigration jails.

Obama in November announced a program to allow roughly 4 million parents of U.S. citizens and legal permanent residents to apply for permission to stay in the country for up to three years and get a work permit. The program mirrors one announced in 2012 that provides protection from deportation for young immigrants brought to the country as children.

A spokesman for Customs and Border Protection, Carlos Diaz, said immigrants caught crossing the border illegally remain a top priority for the agency. The training documents for border agents, he said, "provide clear guidance on immigration enforcement operations so that both time and resources are allocated appropriately."

Crystal Williams, executive director for the American Immigration Lawyers Association in Washington, said the training will help filter people the government said should not be a priority anyway. She said the training marked the first she has heard of officers being directed to screen immigrants for potential leniency before they were arrested.

"Just because it's a change doesn't mean it's anything particularly radical," Williams said.

Rep. Luis Gutierrez, an Illinois Democrat and vocal supporter of Obama's immigration plans, said having CBP officers screen immigrants out of the deportation line lets the government "move criminals and recent arrivals to the front of the deportation line. The emphasis now is on who should be deported first, not just who can be deported."

A former deputy assistant attorney general in the Justice Department, John Malcolm, said the new instructions limit immigration agents.

"Agents are being discouraged away from anything other than a cursory view" of an immigrant's status and qualification for leniency, said Malcolm, who works as a senior legal fellow at the conservative Heritage Foundation think tank in Washington.

Under Obama's plans, the government is focused on deporting immigrants with serious criminal records or who otherwise pose a threat to national security or public safety. For the most part, under the new policy, immigrants whose only offense is being in the country without permission aren't supposed to be a priority for immigration officers.

While the administration has estimated that as many as 4 million people will be eligible for protection from deportation, the Congressional Budget Office estimated about 2 million to 2.5 million immigrants are expected to be approved for the program by 2017. As many as 1.7 million young immigrants were estimated to be eligible for the Deferred Action for Childhood Arrivals program, but since its 2012 creation only about 610,000 people have successfully signed up.

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