Donald Trump has vowed to deport millions of people in his first hour as president of the US.
He has also promised to create a special “deportation force” that would seek to remove all who did not have permission to live and work in the country.
Trump spoke in Phoenix hours after a trip to Mexico at the instance of President Enrique Peña Nieto.
“Anyone who has entered the United States illegally is subject to deportation. We will begin moving them out, day one. My first hour in office, those people are gone,” he said.
“There will be no amnesty.”
Trump, who has been severely criticised over his idea of erecting a wall between the US and Mexico, has insisted that the project is in the interest of his country.
However, the issue of the wall has stirred another round of controversy.
During a press conference at the end of the meeting with the Mexican leader, Trump said the issue of a border wall did come up, but that they did not talk about who would foot the bill.
But Nieto later contradicted him, saying he made it clear that Mexico would not pay for the wall that the billionaire businessman wants to build.
“At the beginning of the conversation with Donald Trump, I made it clear that Mexico will not pay for the wall,” he wrote on Twitter.
Speaking on a television programme moments later, Nieto said Trump posed a threat to his country, and he would not “keep my arms crossed”.
“His policy stances could represent a huge threat to Mexico, and I am not prepared to keep my arms crossed and do nothing,” he said.
“That risk, that threat, must be confronted. I told him that is not the way to build a mutually beneficial relationship for both nations.”
Trump fired back at him, insisting “100%” that Mexico would pay for the wall.
Results of the latest poll conducted by Fox News shows Trump trailing Hillary Clinton, his rival, by two points.