President Trump said Monday that the Democrats are to blame for the caravan of several thousand migrants that's making its way through Mexico to the southern U.S. border.

“Every time you see a Caravan, or people illegally coming, or attempting to come, into our Country illegally, think of and blame the Democrats for not giving us the votes to change our pathetic Immigration Laws!” Trump tweeted Monday morning. “Remember the Midterms! So unfair to those who come in legally.”

[Related: Trump: Democrats figure caravan migrants will vote for them]

More than 7,000 migrants broke through Mexico's southern border and continued on their trek to the United States. Trump said he told the military and U.S. Border Patrol that the caravan headed to the U.S.-Mexican border is now a national emergency.

“Sadly, it looks like Mexico’s Police and Military are unable to stop the Caravan heading to the Southern Border of the United States, “ Trump posted in another tweet. “Criminals and unknown Middle Easterners are mixed in. I have alerted Border Patrol and Military that this is a National Emergy (sic). Must change laws!"

Trump said aid to Central American countries would now be cut off or curtailed after they failed to rein in their own people.

Although Mexico and the U.S. came to an agreement last week on how to proceed with dealing with the 4,000-person caravan that originated in Honduras, the Mexican government and military was unable to stop its progression.

Last week, several members of the caravan that reached the Guatemala-Mexico border tore down the border fences and charged over a bridge into Mexico.

Mexico requested that the United Nations High Commissioner for Refugees establish shelters at its border with Guatemala to house migrants. There, the UNHCR could vet those attempting to migrate north for legitimate claims to refugee status.

In the deal between the U.S. and Mexico, those deemed to have legitimate asylum claims would be transported to a host country that has an agreement with the UNHCR, including the U.S.