Taking drastic action over illegal immigration, President Donald Trump moved Saturday to cut direct aid to El Salvador, Guatemala and Honduras, whose citizens are fleeing north and overwhelming U.S. resources at the southern border.

The State Department notified Congress that it would look to suspend 2017 and 2018 foreign aid payments to the trio of nations, which have been home to most of the migrant caravans that have marched through Mexico to the U.S. border.

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Trump has turned these massive caravans into the symbol of the dangers of illegal immigration — a central theme of his midterm campaigning last fall. With the special counsel’s Russia probe behind him, Trump has revived his warnings of the caravans’ presence.

Trump also has returned to a previous threat he never carried out — closing the border with Mexico. He brought up that possibility on Friday and revisited it in tweets Saturday, blaming Democrats and Mexico for problems at the border and beyond despite warnings that a closed border could create economic havoc on both sides.

“It would be so easy to fix our weak and very stupid Democrat inspired immigration laws,” Trump tweeted Saturday. “In less than one hour, and then a vote, the problem would be solved. But the Dems don’t care about the crime, they don’t want any victory for Trump and the Republicans, even if good for USA!′

As far as Mexico’s role, he tweeted: “Mexico must use its very strong immigration laws to stop the many thousands of people trying to get into the USA. Our detention areas are maxed out & we will take no more illegals. Next step is to close the Border! This will also help us with stopping the Drug flow from Mexico!”

When reporters asked Trump on Friday what closing the border could entail, he said “it could mean all trade” with Mexico and added, “We will close it for a long time.”

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Trump has been promising for more than two years to build a long, impenetrable wall along the border to stop illegal immigration, though Democrats in Congress have refused to provide the money he needs. In the meantime, he has repeatedly threatened to close the border, but this time, with a “mother of all caravans” heading towards the U.S. , he gave a definite timetable and suggested a visit to the border within the next two weeks.

A substantial closure could have an especially heavy impact on cross-border communities from San Diego to South Texas, as well as supermarkets that sell Mexican produce, factories that rely on imported parts, and other businesses across the U.S.

The U.S. and Mexico trade about $1.7 billion in goods daily, according to the U.S. Chamber of Commerce, which said closing the border would be “an unmitigated economic debacle” that would threaten 5 million American jobs.

A group of House Democrats visiting El Salvador denounced the administration’s decision to cut U.S. payments to the region.

The Trump administration has threatened before to scale back or cut off U.S. assistance to Central America, but it’s warnings were largely ignored. Congress has not approved most of those proposed cuts, however, and a report this year by the Congressional Research Service said any change in that funding would depend on what Congress does.

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Short of a widespread border shutdown, Homeland Security Secretary Kirstjen Nielsen said the U.S. might close designated ports of entry to re-deploy staff to help process parents and children. Ports of entry are official crossing points that are used by residents and commercial vehicles. Many people who cross the border illegally often use legal loopholes to request asylum under U.S. law, which does not require asylum seekers to enter at an official crossing.

Border officials are also planning to more than quadruple the number of asylum seekers sent back over the border to wait out their immigration cases, said an administration official. The official said right now about 60 migrants per day are returned and officials are hoping to send as many as 300 per day.

Mexican President Andres Manuel Lopez Obrador said Friday his country was doing its part to fight human trafficking. Criminals charge thousands of dollars a person to move illegal immigrants from Central America through Mexico, increasingly in large groups toward remote sections of the border.

“We want to have a good relationship with the government of the United States,” Lopez Obrador said. He added: “We are going to continue helping so that the migratory flow, those who pass through our country, do so according to the law, in an orderly way.”

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The Associated Press contributed to this article