Trump now says Congress must act to keep southern border open

President Trump followed with more threats on Saturday, tweeting that he would close the border and that the move would "help us with stopping the drug flow from Mexico".

Trump has been putting pressure on Mexico and the Central American countries of Honduras, Guatemala, and El Salvador to stop the migrant flow.

"I don't want to comment on it because we are playing right now - what you want to do is stop the emergency and the breakdown, and you want to try to limit whatever harm that does", he said.

There are signs that the shutdown is being progressively implemented, with Homeland Security Secretary Kirstjen Nielsen ordering 750 agents transferred from ports of entry to Border Patrol units rounding up refugee families attempting to enter the U.S. in more remote areas.

Elected leaders from border communities stretching from San Diego to cities across Texas warned that havoc would ensue on both sides of the global boundary if the ports were closed. -Mexican border as unrealistic. It would also prevent thousands of vehicles built in Mexico from landing in U.S. dealer showrooms.

It has also acquiesced to the US Department of Homeland Security's so-called Migrant Protection Protocols, or "Remain in Mexico" policy, which was imposed unilaterally, forcing asylum seekers to stay across the border in Mexico until their cases are heard, a process that can take months or even years.

That means that workers in auto assembly plants would be out of work, and workers in USA vehicle parts plants would follow, since with assembly plants shut down, parts plants would be idled, too. With Mexico known to be the number one supplier of avocados to the USA, media quickly predicted fruit shortages in the country which in turn sent shock waves on Twitter.

There was a scramble inside the White House on Monday over President Donald Trump's threat to shut down the southern border, three people familiar with what happened tell CNN.

There has been a massive increase of immigrants coming from Central American countries, as over 3,700 immigrants trying to cross illegally into the U.S. were apprehended by U.S. Customs and Border Patrol last Monday - the most significant number in a single day in over ten years.

In San Diego - home of the busiest land border crossing in the Western Hemisphere - just the threat of an extended border shutdown hits sentiment, local economic experts told USA TODAY. Areas along the U.S. -Mexico border would experience the most direct impact, but ripple effects could spread beyond the region. Next step is to close the Border!

During a press conference on Tuesday, Senate Majority Leader Mitch McConnell (R-KY) stated that closing down the border could lead to a "potentially catastrophic economic impact on our country", and that he hopes the border is not closed.

"That means long waiting times, long processing times - it's gonna create more cost, ultimately, for the consumer", Saenz says.

"We ended the day yesterday at Otay Mesa (California) with a back-up of 150 trucks that hadn't been processed", the official said.

'As Washington was asleep, Secretary Nielsen made some decisions on border response and decided she needed to oversee those personally. Over the Thanksgiving holiday previous year, Trump claimed he'd already "closed the border" after officials briefly closed the northbound lanes at San Ysidro, California, for several hours in the early morning to bolster security because of concerns about a potential influx of migrant caravan members.