Aerial view marchers
© UnknownAerial view of march to USA.
As a thousands-strong 'caravan' of Central American migrants makes its way to the US border, President Trump warned the migrants to turn back, and promised them "our military is waiting for you" at the border.

"Many gang members and some very bad people are mixed into the Caravan heading to our Southern Border," Trump tweeted on Monday, before addressing the migrants directly: "Please go back, you will not be admitted into the United States unless you go through the legal process. This is an invasion of our Country and our Military is waiting for you!"

Trump's tweet comes as the Pentagon reportedly prepares to deploy some 5,000 troops to the border, where they will bolster the existing National Guard and Customs and Border Patrol presence there.

It also comes one day after Defense Secretary James Mattis announced that the military has already begun moving equipment, including concrete barriers, to positions along the US' 2,000 mile border with Mexico.

Mattis approved a request from Trump last week to send troops to the border, but was expected at the time to deploy only around 800 troops.

Trump has promised to take harsh action against the approaching caravan several times over the last few weeks. The President first threatened to cut off foreign aid to Guatemala, Honduras and El Salvador if they failed to stop migrants leaving for the US. Trump then warned the migrants to turn around in a similar tweet last Thursday, again asking them to apply for citizenship legally "like millions of others are doing."