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.
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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," Mr Spicer said.