President Trump said Tuesday he’ll send troops to strengthen lax security on the Mexican border, since Congress has denied funding for his long-promised “big, beautiful” wall.

“We have very bad laws for our border, and we are going to be doing some things. I’ve been speaking with [Defense Secretary James] Mattis. We’ll be doing things militarily,” Trump told reporters at the White House as he met with the presidents of Latvia, Lithuania and Estonia.

“Until we can have a wall and proper security, we’ll be guarding our border with the military. That’s a big step. We really haven’t done that before, or certainly not very much before.”

The president offered few specifics, but was enraged about the lack of progress on his signature campaign promise — a wall along the Mexican border to keep out illegal immigrants.

Last week, he called for using the Pentagon’s budget to pay for building the wall — arguing it was a national-security priority — despite strict rules that prohibit spending that’s not specifically authorized by Congress.

While sending active members of the military would likely be against Pentagon regulations short of a foreign invasion, sending National Guard troops to the border would be legal and has been done before.

In 2006, under Operation Jump Start, 6,000 troops were sent to the border to increase security and surveillance.

National Guard troops assisted border-patrol agents with non-law-enforcement duties while additional border agents were hired and trained.

The number declined during the second year to about 3,000.

Over the two years, more than 30 miles of fencing and 13 miles of road were built, and more than 86 miles of vehicle barriers were installed.

The Department of Homeland Security, Pentagon and White House did not immediately respond to requests for comment on how the plan might work.

Trump accused Democrats of allowing “open borders, drugs and crime” and warned Mexico to halt the passage of “caravans” of immigrants or risk US abandonment of the North American Free Trade Agreement.

Trump announced last year that he was ending the Deferred Action for Childhood Arrivals program, which protects young immigrants brought into the country illegally as children.

But DHS is continuing to issue DACA renewals because of a court order.

The caravan Trump referred to once numbered 1,150 or more, but actually halted days ago in the town of Matias Romero.

After days of walking along roadsides and train tracks, the organizers now plan to try to get buses to take participants to the final event, an immigrants’-rights conference in the central state of Puebla later this week.

Trump also railed at his predecessor and congressional Democrats for what he said were weak immigration laws.

“It’s like we have no border,” he said. “We had Obama make changes. The laws that were created by Democrats are so pathetic and so weak.”

Trump has been seething since realizing the $1.3 trillion spending bill he signed last month barely funds the border wall.

Additional reporting by Yaron Steinbuch and AP