US President Donald Trump has called for speedy deportations that bypass any judicial process in a tweet on Sunday.
"When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came," Mr Trump wrote.
His comments come days after Mr Trump reversed a policy to separate migrant children from their parents following fierce backlash at home and abroad.
More than 2,300 children were separated from their parents in May and June.
As of May, all migrants who cross the US border illegally face criminal prosecution under the "zero tolerance" policy.
The president did not make the distinction between economic migrants and those seeking asylum.
Mr Trump has faced criticism, including from his own Republican Party, for his choice of language on Twitter.
When he earlier said immigrants threatened "to pour into and infest our Country", Republican congresswoman Ileana Ros-Lehtinen tweeted back at him saying his "baseless rhetoric" was "repugnant" and dehumanised those looking for a better life.
On 20 June, Mr Trump backed down from his support for the policy and signed an executive order ending the practice of separating families.
He said at the time: "I did not like the sight or feeling of families being separated."
Mr Trump's directive allows for long-term detention of immigrant children (albeit with their parents), which violates federal law that limits child detention to 20 days.