US President tells Republicans to "go nuclear" to stop the flow.
Donald Trump says illegal immigrants should no longer be allowed to obtain work permits in the United States after reports suggested the numbers crossing the Mexican border are rising.
Trump warned trade deals with Mexico would be off if the crossings don't slow down.
"Mexico has got to help us at the border," he said. "If they're not going to help us at the border, it's a very sad thing. Mexico has got help us at the border. And a lot of people are coming in because they want to take advantage of DACA. And we're going to have to really see."
The President's comments follow news reports that a caravan of 1500 migrants is making its way towards the United States.
Many of those travelling come from Central America.
"The bad thing is walking," said one woman from Honduras. "I've spent five days walking day and night without stopping."
On Twitter, Trump called on Republican congressman to "go nuclear" to stop the flow. He wants to fulfill a campaign promise to make Mexico pay for a frontier wall.