President Donald Trump has said the US will “begin cutting off” foreign aid to Guatemala, Honduras and El Salvador because of a large convoy of migrants heading north.
Mr Trump criticised the countries on Monday for allowing people to leave the region and come “illegally” to the US.
The group is travelling through Mexico, but is still far from the US border.
Human rights organisations have said that cutting aid would make the situation worse.
The president has not specified what money will be cut and it is unclear if such action can be taken by presidential order.
Guatemala, Honduras and El Salvador were not able to do the job of stopping people from leaving their country and coming illegally to the U.S. We will now begin cutting off, or substantially reducing, the massive foreign aid routinely given to them.
— Donald J. Trump (@realDonaldTrump) October 22, 2018
In 2017, Guatemala received over $248m (£191m) in US aid. The same year, Honduras received $175m and El Salvador $115m, according to the US Agency for International Development.
“Cutting aid to refugee-producing countries will only make worse the conditions that displace people in the first place,” said Human Rights Watch on Sunday.
The organisation said root causes must be addressed. “People generally don’t want to leave their homes if they can live normal, safe lives there.”
Though President Trump has accused the migrants of trying to illegally enter the US, many of the families travelling towards the border are seeking asylum.
They say they are fleeing persecution, poverty and violence in their home countries.
Women feel safer in a convoy By the BBC’s Aleem Maqbool in Mexico
The square in Tapachula – the first major population centre inside Mexico for these migrants – has turned into what looked like a makeshift camp. Along one side, ambulances lined up so medics could treat those who had become sick or got injured on their journey.
Mexicans came to offer food, water and clothes to the many hundreds of Hondurans who rested ahead of the long punishing journey that still remains ahead of them to the US border.
Many women among the group in particular have told us that they could never have made this journey alone, because it would have been too dangerous. So in spite of their tiredness, they are glad to be with others.
But there is a sense that this is no longer just a convoy of those here in Tapachula, but that there is now a long stream of people stretching back along the route through Guatemala to Honduras, with people stuck at various obstacles and others who are still coming to join this migration.
Why is President Trump reacting so strongly?
Curbing illegal immigration was one of the main campaign promises Mr Trump made when he ran for president.
His Republican Party is facing mid-term elections on 6 November and could be unseated by Democrats in the House of Representatives.
Without offering evidence, Mr Trump has repeatedly suggested the caravan was politically motivated.
On Monday he urged people to blame Democrats for the border crisis, saying: “Remember the mid-terms”.
He also tweeted that the caravan contained “criminals and unknown Middle Easterners”. When he was later pressed by journalists on what this meant, he offered no origin for the claim but invited reporters to investigate for themselves.
Where are the migrants now?
On Sunday, the migrant caravan reached the town of Tapachula, approximately 37km (23 miles) from Mexico’s southern border with Guatemala.
The Mexican authorities had earlier tried to stop them at a border bridge, but some managed to cross into Mexico illegally by boat over the Suchiate river.
Many of them had become aware of the caravan after a former lawmaker had published a poster announcing the caravan on Facebook. News of it quickly spread on social media.
They have since been joined by other Central American nationals as they crossed Guatemala towards the Mexican border.
The region has one of the highest murder rates in the world and many try to flee gang violence.