The move came after President Donald Trump threatened to use military force to completely close the US-Mexico border over the issue.

He also said aid could be cut to countries allowing the caravan to pass.

The group of Salvadoreans, Hondurans and Guatemalans say they are fleeing violence and poverty.

Mr Trump has previously threatened to cut Honduran aid. The US sent more than $175m to the country in 2016 and 2017, according to the US Agency for International Development.

The president's threats also come just weeks before the mid-term elections on 6 November, which could see Democrats unseating Republicans in Congress.

Mr Trump's recent comments are being viewed as an effort to bolster support among his base by cracking down on migration.

Mexico's main reaction has been to step up security on its southern border with Guatemala. Hundreds of federal police officers and immigration officers have been sent to the porous border region along the Suchiate River which divides the two neighbours.

In part, the response is intended to both dissuade the migrants from even attempting to enter Mexico and potentially to show the Trump administration that Mexico is willing to, as the government put it, "maintain order".

Beyond that, this situation catches Mexico at a strange time. One administration, that of President Enrique Peña Nieto, is leaving office and the new one, of President-elect Andres Manuel Lopez Obrador, isn't yet through the door.

Migrant caravans of this type are nothing new, they quite often take place. However, this one, coming as it does so close to the US mid-term elections in November, has taken on a highly political dimension, to that point that President Trump has threatened to use the military and close the US southern border.

The group of Central American migrants has made its intentions clear: they are heading to the US.

Since he was on the campaign trail, Mr Trump has lambasted illegal immigrants, and this latest caravan comes after a major crackdown on migrants heading over the Mexican border.

Changes to detention rules saw thousands of migrant children detained and separated from their parents earlier this year, sparking national and international condemnation.

BBC