Amplified by conservative media, Trump has turned the caravans into the symbol of what he says are the dangers of illegal immigration — a central theme of his midterm campaigning last fall. With the special counsel's Russia probe seemingly 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."
Trump has been promising for more than two years to build a long, impenetrable wall along the border to stop illegal immigration, though Congress has been reluctant to provide the money he needs. In the meantime, he has repeatedly threatened to close the border, but this time, with a new group of migrants heading north , 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.
Sen. Bob Menendez, D-N.J., ranking member of the Senate Foreign Relations Committee, spoke out Saturday against cutting off aid to Central America, declaring that "foreign assistance is not charity; it advances our strategic interests and funds initiatives that protect American citizens."
And a group of House Democrats visiting El Salvador denounced the administration's decision to cut aid to the region.
"As we visit El Salvador evaluating the importance of U.S. assistance to Central America to address the root causes of family and child migration, we are extremely disappointed to learn that President Trump intends to cut off aid to the region," said the statement from five lawmakers, including Rep. Eliot L. Engel of New York, who chairs the House Foreign Affairs Committee. "The President's approach is entirely counterproductive."
The Trump administration has threatened before to scale back or cut off U.S. assistance to Central America. 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.
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 ultimately 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. The official was not authorized to speak publicly about internal plans and spoke to The Associated Press on condition of anonymity.
Mexican President Andres Manuel Lopez Obrador said Friday his country was doing its part to fight migrant smuggling. Criminal networks charge thousands of dollars a person to move migrants 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."
Marcelo Ebrard, Mexico's foreign relations secretary, tweeted that his country "doesn't act based on threats" and is "the best neighbor" the U.S. could have.
Alejandra Mier y Teran, executive director of the Otay Mesa Chamber of Commerce in San Diego, said the mere threat of border closures sends the wrong message to businesses in Mexico and may eventually scare companies into turning to Asia for their supply chains.
"I think the impact would be absolutely devastating on so many fronts," said Mier y Teran, whose members rely on the Otay Mesa crossing to bring televisions, medical devices and a wide range of products to the U.S. "In terms of a long-term effect, it's basically shooting yourself in your foot. It's sending out a message to other countries that, 'Don't come because our borders may not work at any time.' That is extremely scary and dangerous."
Merchant reported from Houston, Lucey from Washington. Associated Press writers Peter Orsi in Mexico City, Elliot Spagat in San Diego and Colleen Long, Catherine Lucey and Matthew Lee in Washington contributed to this report.