Donald Trump has been visiting Southern California to hammer home his message that more fencing is needed to prevent illegal immigrants entering from Mexico.
The US President is seeking to divert money from other federal funds to construct the barriers after failing to get Congress backing for the project. He also promised extra military sources for the border.
"The system is full and when it's full, there's nothing you can do,” he said. “You have to say 'I'm sorry we can't take you.' We've been trying to take people, and I have to disagree with it. We've been trying to take people, and you can't do it. You can't do it."
Trump also threatened to raise tariffs against Mexico if it fails to combat drug trafficking. Opponents accuse him of raising the issue to slur migrants who have no connection with professional drug running operations.