U.S. President Donald Trump is once again sounding off on migrant caravans.
On Twitter this week, the president appeared to threaten the newly minted Canada-U.S.-Mexico trade deal over a caravan of Honduran migrants trying to reach his country.
READ MORE: Trump appears to threaten USMCA deal when lashing out at migrant caravan
“The assault on our country at our Southern Border, including the Criminal elements and DRUGS pouring in, is far more important to me, as President, than Trade or the USMCA,” Trump tweeted.
“Hopefully Mexico will stop this onslaught at their Northern Border.”
This is far from the first time Trump has spoken out against the caravans. Here’s a look at what exactly the caravans are — and why they upset Trump so much.
What are migrant caravans?
“Migrant caravans” is the name attributed to groups that travel from Central America in an attempt to make their way through Mexico and eventually into the U.S.
Currently, about 3,000 Hondurans are making their way through Guatemala. More Honduran migrants tried to join a caravan Wednesday, and it has been steadily growing in size since it departed the Honduran city of San Pedro Sula on Saturday.
WATCH: Honduran migrants push through Guatemalan jungle as Trump threatens to send military
The caravan, fairly compact in recent days, has dispersed a bit, with different bands of people seen walking together in a line, some boarding buses or trying to hitch rides.
The migrants hope to reach Mexico and then cross its northern border with the United States, to seek refuge from lawlessness and poverty.
READ MORE: Donald Trump threatens to take away aid from Honduras unless migrant caravan is stopped
How does Trump respond to these caravans?
Trump has repeatedly uttered threats over the caravans. His latest threat placed the USMCA in jeopardy, he also threatened to deploy the military and close the southern U.S. border. In the past, he has threatened to revoke aid from Honduras.
Under Trump, the U.S. has already sought to sharply decrease aid to Central America. But Honduran President Juan Orlando Hernandez told Reuters that cuts in U.S. aid would make it harder to stem illegal immigration.
Trump has also said those who try to come into the U.S. via these caravans will not be welcomed and has blamed “weak laws” on Democrats.
WATCH: Family fleeing poverty, violence in Mexico’s migrant caravan seek American dream
The president often puts the responsibility of stopping caravans solely on Mexico.
“Mexico has the absolute power not to let these large ‘Caravans’ of people enter their country,” he tweeted in April.
READ MORE: Donald Trump appears to threaten ‘cash cow NAFTA’ over Mexico ‘migrant caravan’
So, why do people join the caravans?
This current migrant exodus follows a similar caravan of Central Americans that started out from southern Mexico last March and that ultimately led to hundreds of migrants either seeking asylum in the United States or remaining in Mexico.
Many of the migrants on that trek were Hondurans. Central Americans followed it closely in the media, in part due to Trump’s repeated criticism of it. That publicity raised the profile of caravans as a potentially safer way to reach Mexico or the United States.
WATCH: Caravan of migrants seeking asylum reaches U.S.-Mexico border
Migrants are fleeing from some of the poorest countries in the Americas, and the most violent in the world.
Economic desperation and fear of brutal street gangs known as Maras are consistently cited by migrants as incentives to leave in spite of the costs of paying people traffickers, the risks of deportation, being robbed or even killed en route.
— With files from Reuters, The Associated Press