United States President Donald Trump has announced his intention to trim down aid given to three Central American nations due to their failure in stopping a large immigrant caravan passing through their borders to reach the US.

Trump declared the decision on Twitter Monday after casting blame on Democrats for poor immigration laws, further urging followers to vote in the Midterm elections.

The president expressed his doubt in Mexico's ability to effectively stop the caravan, he referred to as "criminals and unknown Middle Easterners," adding that "I have alerted Border Patrol and Military that this is a National [Emergency]".

The US has given more than an estimated $200 million in aid to Guatemala, $164 million to Honduras and $113 million to El Salvador from 2016 to 2017, as part of different aid programs. 

Different US administrations have long claimed that the programs are a way to improve critical infrastructure and social conditions in impoverished Latin American countries, ultimately seeking to stifle immigration coming through the US/Mexico border.

The Trump administration, however, cut nearly 40 percent in aid given to the South American countries in its 2017 budget, focusing more on strengthening border security in a controversial move seen by some observers as a likely cause for more immigration.

The current large caravan of immigrants heading upwards through Latin American first started its passage on October 12 in the Honduran city of San Pedro Sula with a number of allegedly less than 200 people. The group quickly amassed more immigrants as the caravan progressed further up-north, passing beyond Guatemala and El Salvador. UN spokesman Farhan Haq has estimated the caravan includes more than 7,000 people after reaching Mexico.

The caravan is still about 1,800 kilometers south of the US border, while Mexican authorities hope to break down the large assembly by requesting that the immigrants apply for asylum in the country or to face deportation to their respective countries.