US President Donald Trump has directed his administration to enforce the nations immigration laws more aggressively, unleashing the full force of the federal government to find, arrest and deport those in the country illegally, regardless of whether they have committed serious crimes.

Documents released on Tuesday by the Department of Homeland Security (DHS) revealed the broad scope of the President's ambitions: to publicise crimes by undocumented immigrants, strip such immigrants of privacy protection, enlist local police officers as enforcers, erect new detention facilities, discourage asylum seekers and, ultimately, speed up deportations, the New York Times reported.

Undocumented immigrants arrested for traffic violations or shop-lifting will be targeted along with those convicted of more serious crimes. 

The memos do not alter US immigration laws, but take a much tougher approach towards enforcing existing measures.

There are an estimated 11 million illegal immigrants in the US. 

White House Press Secretary Sean Spicer said on Tuesday the new guidelines would not usher in mass deportations, but were designed to empower agents to enforce laws already on the books.

"The President wanted to take the shackles off individuals in these agencies," Spicer said.

"The message from this White House and the Department of Homeland Security is that those people who are in this country, who pose a threat to our safety, or who have committed a crime, will be the first to go," he added.

Major steps outlined in the papers included hiring more Customs and Border Protection agents, expanding a programme that gives DHS Secretary John Kelly more power in directing field operations, initiating a wall along the US-Mexican border, and stepping up the effort to "return aliens to contiguous countries".

The guidelines revealed sweeping changes from the approach taken by former President Obama. The only Obama policy that survived was Deferred Action for Childhood Arrivals (DACA), a programme that allowed people who entered the country illegally as children to stay, usually for work or school, the Hill magazine reported.

But the White House said that even ­DACA could be ultimately eliminated as Trump seeks a tough approach.

Meanwhile, a banner reading "Refugees Welcome" was unfurled atop the pedestal of the Statue of Liberty on Tuesday, after the DHS announced expanded immigration enforcement policies. National park police officers were investigating how the banner got on, NBC News reported.

The banner was affixed by nylon rope to the wall of the public observation deck at the base of the statue. It was later taken down by park rangers.

A social media account "Alt Statue of Liberty", who claimed responsibility for the stunt, said: "We have no formal group — just private citizens who felt like we needed to say something about the America we believe in."