President Donald Trump on Monday vowed to send as many troops as necessary to the U.S.-Mexico border to block the growing caravan of people from Honduras, El Salvador, and Guatemala as they make their way through Mexico to the nation. He called the trek “an assault on our country.”

“I have alerted Border Patrol and Military that this is a National Emergy,” he wrote in a Tweet. “Must change laws!”

Trump also said he will cut aid to the three Central American countries for letting their people migrate to the U.S.

“We have been giving so much money to so many different countries for so long that it’s not fair and it’s not good. And then when we ask them to keep their people in their country, they’re unable to do it,” he said Monday at the White House.

However, there were no indications of any actions on cutting aid to the countries across his administration at present, according to an AP report. White House officials were unable to give an explanation for the president’s tweet. Federal agencies told the news agency there was no guidance on the president’s declaration yet.

In a series of tweets, Trump also blamed the Democrats for not allowing his administration to change the immigration law. 

“I think this could be a blessing in disguise because it shows how bad our laws are,” he said. “The Democrats are responsible for that.”

Even though Mexico ordered the migrants to submit to processing by the immigration authorities at a legal border crossing, thousands chose to move on ahead without it.

According to Mexican officials, migrants seeking asylum were not under any legal obligation to apply in Mexico, New York Times reported.  Though officials on Sunday urged migrants to apply for asylum or seek legal immigration status in Mexico, they made little effort to halt migrants as they walked along the main highway, it added. The procession moved forward while federal police officers monitored it at times and a police helicopter circled overhead. As the caravan walked through Mexico, some helped them by handing out food and sometimes clothes, reports said.

According to Trump, “criminals and unknown Middle Easterners” were “mixed in” the caravan of 7,000 that is heading toward the U.S. in hope of asylum, but he declined to comment on whether the assumption was based on intelligence agencies or some other source, a report in USA Today said.

AP reporters who have been traveling with the caravan for more than a week said they didn’t meet any “Middle Easterners.” 

The caravan is made up of young men, women, and children fleeing the poverty, violence, and corruption in their countries. Usually, caravans are formed by Mexican advocacy groups to draw attention to the plight of asylum seekers. This one started off in Honduras when about 160 people left the gang-plagued city of San Pedro Sula.

If Trump actually cut aid to the three countries, it will push them further into the very situations people fled from. But, it is the Congress and not the president that appropriates aid money.

“My colleagues and I will not stand idly by as this administration ignores congressional intent,” Rep. Eliot Engel, the top Democrat on the House Foreign Affairs Committee, said Monday.

“If you take that money away or you make it unpredictable, you’re actually going to foster the very conditions that are driving people toward migration,” Paul O’Brien, the vice president for policy and advocacy at Oxfam America, told AP while accusing Trump of “essentially seeking to use migrants as a political chip.”

“No one is capable of organizing this many people. Nobody,” Irineo Mujica of Pueblo Sin Fronteras (People Without Borders) said. “It’s an exodus.”

The group of 160 grew to more than 1,600 by the time it reached the Guatemalan border. For migrants, caravans are seen as a better and safer option than going on their own or in small groups.

Vice President Mike Pence said in a tweet the caravan was made “up of many vulnerable families, children and elderly being exploited by human traffickers and criminal gang members.”

“We must secure our border, build the wall, close the loopholes, & fix this broken immigration system once and for all. Remember the Midterms!” he added.