Donald Trump details plan for tougher US entry for migrants

The president, speaking in the Roosevelt Room of the White House, told reporters, "we have no choice".

"We will defend our borders and we will defend our country."

He added, "no nation can allow itself to be overwhelmed by uncontrolled people rushing our border."

Trump, whose core supporters back a tough line on immigration, later told reporters, "they're throwing rocks viciously and violently.

"You saw that three days ago...really hurting the Mexico military...we're not going to put up with that...they want to throw rocks at our military, our military fights back."

He added, "when they throw rocks like they did at the Mexico military and police, I say consider it a rifle."

Trump had earlier repeated his claim that a caravan of thousands of Central American migrants heading to the US-Mexico border is "like an invasion".

The president added that the "illegal aliens" should "turn back now".

He claimed the caravan of migrants is causing "a crisis on our southern border" and said, "this is a perilous situation that will become even more hazardous."

Trump has unveiled his immigration policy ahead of the midterm elections on 6 November.

His successful 2016 presidential campaign had a strong focus on border security.

Trump told reporters on Thursday that immigrants "cost our country billions and billions of dollars each year", adding that they put an "enormous strain on our local schools, hospitals and communities in general".

The president said earlier on Thursday that the number of troops deployed to the US-Mexico border could reach 15,000.

The figure took the Pentagon by surprise as it had only planned to send 7,000 troops to support Customs and Border Protection agents.

Trump has also hinted that State Department spokeswoman Heather Nauert is "under very serious consideration" to be the next US ambassador to the UN.