PALM BEACH, Fla. — Threatening drastic action against Mexico, President Donald Trump declared on Friday he is likely to shut down America’s southern border next week unless Mexican authorities immediately halt all illegal immigration. Such a severe move could hit the economies of both countries, but the president emphasized, “I am not kidding around.”

“It could mean all trade” with Mexico, Trump said when questioned by reporters in Florida. “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 surge of migrants heading north, he gave a definite timetable.

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.

Trump tweeted Friday morning, “If Mexico doesn’t immediately stop ALL illegal immigration coming into the United States through our Southern Border, I will be CLOSING the Border, or large sections of the Border, next week.”

In Florida, he didn’t qualify his threat with “or large sections,” stating: “There is a very good likelihood I’ll be closing the border next week, and that is just fine with me.”

He said several times that it would be “so easy” for Mexican authorities to stop immigrants passing through their country and trying to enter the U.S. illegally, “but they just take our money and ‘talk.’”

A senior Homeland Security official suggested Trump was referring to the ongoing surge of mostly Central American families heading north through Mexico.

Short of a widespread shutdown, the official said the U.S. might close designated ports of entry to redeploy staff to help process parents and children.

Ports of entry are official crossing points that are used by residents and commercial vehicles. The official, who spoke to reporters on condition of anonymity, did not specify which ports the administration was considering closing, but said only that closures were “on the table.”

Trump’s latest declaration came after Mexican President Andres Manuel Lopez Obrador said his country was doing its part to fight migrant smuggling.

“We want to have a good relationship with the government of the United States,” Lopez Obrador said Friday. 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.