The United States said on Monday it will send over 5,200 troops to help secure the border with Mexico, a far larger-than-expected deployment as President Donald Trump hardens his stance on immigration ahead of Nov 6 mid-term elections.

A second caravan of about 3,000 people were at the Guatemala-Mexico border, he added.

Trump railed against illegal immigration to win the 2016 US presidential election. Trump said the US would build "tent cities" to house migrants seeking asylum, rather than releasing them while they await court decisions.

Central American migrants, part of a caravan trying to reach the US, use a provisional ladder to climb down from the bridge that connects Mexico and Guatemala to carry on their journey in Ciudad Hidalgo in Mexico on October 20, 2018. Photo: Reuters

US Custom and Border Protection agents with full riot gear take part in a drill to protect the crossing gates against people who want to cross the border illegally on the international bridge between Mexico and the US, in Ciudad Juarez, Mexico on October 29, 2018. Photo: Reuters