The Trump administration, intensifying its showdown with sanctuary cities, plans to send Border Patrol agents into interior parts of the country to assist federal agents in routine immigration arrests and deportations.

About 100 reassigned U.S. Customs and Border Protection agents, some of whom have tactical training and often work to arrest high-level smugglers and drug traffickers along the border, are expected to start helping Immigration and Customs Enforcement agents beginning this month. The move was confirmed Friday by Immigration and Customs Enforcement’s acting director Matthew Albence.

The agency did not disclose the locations where the employees would be sent, but several news organizations, including the New York Times, which first reported the story, named the Bay Area as a possibility, along with Los Angeles, New York, Chicago and Boston. The bumped-up staffing will not be limited to sanctuary cities, though much of it will be located there.

“As we have noted for years, in jurisdictions where we are not allowed to assume custody of aliens from jails, our officers are forced to make at-large arrests of criminal aliens who have been released into communities. This effort requires a significant amount of additional time and resources,” Albence said.

The Trump administration, which has tried to toe a tough line on illegal immigration, has increasingly taken issue with cities that have refused to cooperate with immigration enforcement, places known as sanctuary cities.

The president has sought to portray communities that don’t hand over undocumented residents to ICE as having higher levels of crime. He recently used his State of the Union speech to highlight the rape of a 92-year-old New York City woman by an undocumented 21-year-old who had been previously arrested but then was released.

Cities like San Francisco and Oakland, which have had sanctuary policies in place for years, argue that targeting undocumented residents who have not committed crimes only makes their communities less safe. With the threat of deportation, these residents are not as likely to report crimes and cooperate with local police.

Oakland Mayor Libby Schaaf was quick to criticize the deployment of Border Patrol agents to the Bay Area as both unproductive and cruel.

“I’m hopeful that these special forces will not set foot in Oakland,” Schaaf said. “If they do, we have a very compassionate and prepared community that is ready to wrap their arms around our neighbors.”

ICE agents generally target undocumented residents with criminal backgrounds, though stings often include arrests of people who have done nothing wrong other than be in the country illegally.

The agency made a request for reinforcements from Customs and Border Protection because its agents have not been able to keep up with their workload, especially in the places where police and sheriff’s deputies are prohibited from assisting ICE with many of their exercises.

ICE did not specify what agents it wanted from Customs and Border Protection, but at least some of the employees being sent are from the Border Patrol Tactical Unit, also known as BORTAC. This force often deals with the drug trade, terrorism and matters of national security.

BORTAC agents are not expected to engage in special missions in their new assignment, only provide assistance and backup to ICE with everyday arrests and deportations.

“While some of them are trained in tactical operations, that is one of the many areas of training. These officers have also been trained in routine immigration enforcement actions which is what they have been asked to do,” read a statement from the Department of Homeland Security.

The additional staffing for ICE is the latest effort by the Trump administration to play tough with sanctuary communities.

The Justice Department joined the offensive shortly after the president took office, attempting to withhold federal funds from certain cities, including San Francisco. Just this month, the agency sued local and state governments in California, Washington and New Jersey over immigration matters. The California suit takes aim at a state ban on private detention facilities, including those run by ICE.

ICE has announced stepped-up policing of undocumented residents in sanctuary cities before, though the crackdowns have not always materialized.

Terri Givens, who tracks immigration policy as a Menlo Park political scientist and CEO of the Center for Higher Education Leadership, says whether or not the federal efforts are successfully carried out, they have a chilling effect on the communities they target.

“It’s hard to say what’s going to happen from a procedural prospective until the operation has been here for a bit,” Givens said about Friday’s announced action. “But it definitely creates an air of fear.”

These “scare tactics,” she said, can sometimes be enough to convince would-be immigrants not to cross the border and even make some undocumented residents consider leaving.

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander