President Donald Trump threatened on Thursday to deploy the military and close the southern USA border if Mexico does not halt a caravan of Central America migrants heading north, raising the risk of huge disruptions to trade.
Trump also threatened to upend a pending trade deal with Mexico that took more than a year to negotiate and is created to replace the North American Free Trade Agreement.
He also threatened to send in the USA military to "CLOSE OUR SOUTHERN BORDER!" and keep out "MANY CRIMINALS" among the migrants.
Changes to detention rules saw thousands of migrant children detained and separated from their parents earlier this year, sparking national and global condemnation.
A first group of several hundred migrants arrived late on Wednesday in the border town of Tecun Uman, Guatemala, where they overflowed a local shelter, leaving many to sleep in the town square or on the street, an AFP correspondent said. Any who are determined to have a legitimate claim will begin the process of being placed in a host country - which may or may not be the US - and the rest will be sent packing.
Launched Saturday from Honduras, the caravan reportedly has grown to more than 4,000 people, including whole families and - in some cases - children traveling without their parents.
Mexican authorities are particularly wary of migrants attempting to cross the Suchiate River that forms the southwestern border with Guatemala, a popular illegal route into Mexico.
On Thursday, Mexico's foreign ministry said the government was assisting members of the caravan who had already crossed into Mexican territory.
They plan to cross Mexico's border in the coming days, then continue north to the United States. Some hope to eventually enter the United States to escape violence and poverty in Central America.
However, he added that only 15 of 132 Central Americans registered in the town had come from the caravan.
The threats follow a similar playbook he used in April, when a caravan of around 1,500 took a similar journey.
Honduran migrants, part of a caravan trying to reach the USA, line up to enter a migrant shelter in Guatemala City, Guatemala October 17, 2018.
In addition to this latest caravan now at the Mexico-Guatemala border, a USA border patrol official tells CBS News there has been an increase in large groups attempting to cross into the US together.
Those who apply for refugee status will be vetted by United Nations officials at the immigration shelters on the border.
He tweeted on Tuesday: "The United States has strongly informed the President of Honduras that if the large Caravan of people heading to the U.S.is not stopped and brought back to Honduras, no more money or aid will be given to Honduras, effective immediately!"
"Whoever wants to work in our country is going to have support, is going to have a work visa", he said.
"We have evidence that this caravan is also very much politically motivated", he claimed.