Migrants abandoning long walk to US

THE United States will send an additional 5200 troops to help secure the US-Mexico border amid the arrival of the "migrant caravans" of thousands of Central American asylum seekers.

But morale appears to be eroding inside the migrant caravans pushing toward the United States, with members dropping out to return home, some opting to try their luck in Mexico and others demanding "safe and dignified transport", as the endless walking begins to take its toll.

The first of the three caravans attempting the journey is still at least 1600km from the US-Mexico border.

A Fox News crew travelling with the leading caravan on Tuesday observed migrants standing on a bridge outside of the town of Niltepec, hoping to get rides in vehicles, while others looked to get on board buses that lined up.

That caravan is estimated to contain 4000 people - but the number is slowly shrinking as weary travelers drop out or apply for protected status in Mexico, spurring the caravan's leaders to make the request for help with transportation to Mexico's capital, according to the Associated Press.

"Of the friends that I have been with, all want to go back," Hasiel Isamar Hernandez, a 28-year-old mother of three from Honduras, told the news agency.

The White House made the announcement of the extra troops on Monday as President Donald Trump hardens his stance on immigration ahead of November 6 midterm elections.

It is a deployment far larger than expected and will more than triple the current military presence, creating an active-duty force comparable in size to the US military contingent in Iraq.

Before the announcement, Mr Trump tweeted: "Many Gang Members and some very bad people are mixed into the Caravan heading to our Southern Border."

"Please go back," he said, "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!"

Migrants hitch rides on passing trucks, in Niltepec, southern Mexico, as the migrant caravan slowly advances towards Mexico City. Picture: Rebecca Blackwell/AP

A woman carries her infant as migrants line up for rides in a handful of buses helping transport families with young children to the next stop, in Niltepec, southern Mexico. Picture: Rebecca Blackwell/AP

It has also been reported that 241km of concertina wire, also known as barbed wire or razor wire, and military helicopters will be on hand to stop migrants who are trekking through Mexico, to cross the border.

The migrants, many of whom are families travelling with children, are fleeing poverty and violence in Central America.

General Terrence O'Shaughnessy, the head of US Northern Command, said 800 US troops were already en route to the Texas border and more were headed to the borders in California and Arizona as part of the deployment dubbed "Operation Faithful Patriot".

According to The Washington Post,he said the military, working alongside US Customs and Border Protection (CBP), will focus first on "hardening" the border in Texas, followed by Arizona and California.

Children from the migrant caravan wait for a ride on the side of the road in Mexico as the thousands of asylum seekers continue their slow march toward the US border. Picture: Rodrigo Abd/AP

A Mexican Federal Police helicopter flies close to the Suchiate River that connects Mexico and Guatemala, to create a downwash force to discourage migrants from crossing. Picture: Santiago Billy/AP

A helicopter creates dust clouds to discourage people from trying to cross the Suchiate River between Guatemala and Mexico. Picture: Santiago Billy/AP

"That is just the start of this operation. We will continue to adjust the number and inform you of those," General O'Shaughnessy said.

"We'll be able to spot and identify groups and rapidly deploy CBP personnel where they are needed."

US officials have stressed that the troops would not police the border and instead carry out support roles like building tents and barricades and flying US customs personnel to locations along the border, Reuters reported.

Although Mr Trump railed against illegal immigration to win the 2016 US presidential election, if the Republicans lose control of the House of Representatives or the Senate, it could become much harder for the US leader to pursue an anti-immigrant agenda in his remaining two years in office.