Police are not happy about the federal government's push to have them help enforce immigration laws. Above, the family of Fidelino Gomez (right), whose children were born in the U.S., walk outside their home in San Jose Calderas, which has seen an influx since an immigration on an Iowa factory in 2009, May 1, 2012. Jorge Dan Lopez/Reuters

Police across the country have expressed fears President Trump’s immigration policy will make their jobs more difficult, discouraging those who could face deportation from cooperating in criminal investigations.

Trump took his first steps last week, authorizing construction of a wall across the U.S. border with Mexico and banning entry into the United States for at least 90 days from seven Middle Eastern and African countries. He also signed an order denying federal funds to “sanctuary cities” if they fail to cooperate with Immigration and Customs Enforcement.

“It is my job to investigate crimes,” Los Angeles Detective Brent Hopkins told the LA Times. “And if I can’t do that, I can’t get justice for people, because all of a sudden, I’m losing my witnesses or my victims because they’re afraid that talking to me is going to lead to them getting deported.”

The Times reported officers are balking at being required to detain suspected undocumented immigrants, saying immigration enforcement is not part of their job description, and besides, they’re too busy answering emergency calls, arresting criminals and stopping erratic drivers to add immigration enforcement to their list of things to do.

“We have enough issues just trying to keep the peace anyway,” J.C. Duarte, a veteran LAPD officer, told the Times. “It’s just going to create a wedge between immigrants and law enforcement. Whether they’re here legally or not, there’s going to be a fear generated.”

Only about 30 police and sheriff’s agencies nationwide have the authority to back up federal immigration agents, the Associated Press reported, half the number that did in 2009. Perhaps the best-known backer of the program was former Sheriff Joe Arpaio, who used it aggressively in the Phoenix area. The program led to racial profiling of Latinos and a lawsuit that resulted so far has cost the county $50 million.

Police traditionally have stayed out of immigration enforcement. Some 1,600 officers were trained by ICE from 2006 to 2015 but the Obama administration phased out all arrest power in 2013.

The U.S. Conference of Mayors and the Major Cities Chiefs Association issued a joint statement last week expressing “strong reservations” about Trump’s order, saying they need clarification from the Department of Homeland Security and the attorney general to develop an approach that “does not interfere with strong police-community relations or place inappropriate burdens on local police officers and upholds our nation’s immigration laws.”

The Fraternal Order of Police issued a statement in support of immigration enforcement, saying local and federal authorities should cooperate with each other. The statement by FOP President Chuck Canterbury cautioned, however, action cannot be taken that would “compromise the safety of the public.”