Without offering evidence to support the claim, President Donald Trump on Monday contended a large caravan of Central American migrants also includes “unknown Middle Easterners.”

He also threatened to end foreign aid to countries from which most members of the caravan come. That list includes Honduras, Guatemala and El Salvador. Trump has proposed foreign aid cuts before, only to have Republican and Democratic lawmakers reject them and allocate the funds via massive spending bills Trump was forced to sign to avert more government shutdowns on his watch.

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

Mexican law enforcement forces have tried to slow the large group of migrants as they attempt to move through the country toward its border with the United States. Citing violence and a lack of jobs, the migrants are trying to enter the U.S. over the objections of Trump and many Republican lawmakers.

U.S. officials have said most of the members of the group are Hondurans, but now the commander in chief says he has alerted U.S. Border Patrol and military leaders that the caravan’s approach amounts to 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. Criminals and unknown Middle Easterners are mixed in,” Trump wrote in a Monday morning tweet.

Watch: House GOP Candidates Are Shying Away From Trump as Midterm Nears

He did not provide an explanation for the claim, including whether he received the alleged information from U.S. intelligence officials. Trump frequently makes false statements that appeal to and fire up his conservative base; the crucial congressional midterms are just 15 days away.

The president, who last week said he would send active-duty American military troops to secure the U.S.-Mexico border, added he has “alerted Border Patrol and Military that this is a National Emergy [sic].”

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

— Donald J. Trump (@realDonaldTrump) October 22, 2018

Sending active-duty troops to the border for a domestic law enforcement matter would require congressional approval. Both chambers, however, are slated to be in recess until the week after the Nov. 6 elections. The 1878 Posse Comitatus Act bars a sitting president from using the military as a police force, but he could ask the House and Senate to grant him a waiver — though Senate Democrats almost inevitably would block it.

As he prepares for a campaign rally in Houston later Monday for former GOP rival Sen. Ted Cruz where immigration and border security — and that caravan — are sure to come up, Trump ended his first tweet with a demand that Congress “Must change laws!”

With that rally less than 12 hours away, Trump showed again how the congressional elections are never far from his mind.

He told his followers “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!”

The president also is slated to hold rallies Wednesday night in Mosinee, Wisconsin, and Friday night in Charlotte.

“Remember the Midterms!” he wrote Monday. “So unfair to those who come in legally.”

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! Remember the Midterms! So unfair to those who come in legally.

— Donald J. Trump (@realDonaldTrump) October 22, 2018