The administration of US President Donald Trump has announced plans to deploy highly trained tactical border control agents to so-called "sanctuary cities" across the country to boost arrests of undocumented immigrants.

Members of the US Customs and Border Protection's (CBP) Border Patrol Tactical Unit (BORTAC) will be among the officers deployed to cities including Los Angeles, Chicago and New York, to assist Immigration and Customs Enforcement (ICE).

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Officers will also be sent to San Francisco, Atlanta, Houston, Boston, New Orleans, Detroit and Newark, New Jersey, CBP spokesman Lawrence Payne said in a statement on Friday.

The move is the latest escalation in the administration's pressure campaign against cities and towns that have enacted "sanctuary" policies in which local law enforcement do not coordinate with federal immigration officers.

"ICE is utilizing CBP to supplement enforcement activity in response to the resource challenges stemming from sanctuary city policies," ICE acting Director Matthew T Albence said in a statement.

"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."

BORTAC's members undergo a "grueling" training program designed to "mirror aspects" of US Special Operation Forces courses, according to details about the programme published on the CBP website.

The unit was launched in 1984 in response to rioting at immigration detention facilities. Members carry additional gear, including stun grenades, and their training includes sniper certification, according to the New York Times, which first reported the plan. The unit usually conducts operations that are considered high risk and involve suspects known to be violent, according to the newspaper.

Escalating campaign

Trump has made immigration a centrepiece of his re-election campaign and his administration has worked to undermine jurisdictions with sanctuary policies.

On Monday, the Department of Justice filed a number of lawsuits against California, New Jersey and King County, Washington, claiming their policies make it difficult for authorities to enforce federal immigration law.

The Department of Homeland Security said last week it would bar New Yorkers from renewing or obtaining new Global Entry passes - preclearances that allow faster passage through airport immigration - and from participating in three programmes that permit faster travel between the US, Canada and Mexico, which could affect hundreds of thousands of travellers.

The deployment of the tactical agents will run from February through May, the Times reported, citing a CBP email.

'Intimidate and retaliate'

Rights groups, Democratic legislators, and a former CBP official decried the announcement.

The American Civil Liberties Union Nauraeen Shah said the policy "will put lives at risk by further militarising our streets."

Make the Road New Jersey, an immigrant support group, in a tweet accused the Trump administration of "deploying weapons of war to our communities".

Democratic congresswoman Ayanna Pressley, whose district includes Boston, said: "We will not stand for this."

"Let us be clear, this move has nothing to do with public safety, but rather serves only to further the Trump Administration’s agenda to intimidate and retaliate against cities that uphold the dignity and humanity of our immigrant neighbors," she said a statement.

Meanwhile, former CBP Commissioner Gil Kerlikowske told the Times the move was a "significant mistake".

"If you were a police chief and you were going to make an apprehension for a relatively minor offense, you don’t send the SWAT team. And BORTAC is the SWAT team," Kerlikowske to the newspaper. "They’re trained for much more hazardous missions than this."