President Donald Trump is ripping a page from the Obama playbook in planning to send U.S. troops to the southern border with Mexico.

Speaking at a lunch with Baltic leaders on Monday, Trump said he had discussed the idea with Defense Secretary Jim Mattis, and “we’re going to do some things militarily. Until we can have a wall and proper security, we’re going to be guarding our border with the military. That’s a big step.”

The president’s abrupt announcement — coming during a meeting that was supposed to focus on NATO and Russia — comes a day after administration officials said they were working on a legislative package aimed at closing immigration “loopholes.” Trump tweeted earlier this week that Republican lawmakers should pass a border bill using the “Nuclear Option if necessary” to ram it through.

He doubled down in an afternoon press conference with the leaders of Lithuania, Estonia, and Latvia, telling reporters that “we are preparing for the military to secure our border, we have a meeting on it in a little while with general Mattis and everybody.”

The president has recently floated the idea of having the Pentagon, at least in part, pay for the wall along the U.S./Mexico border, which he has previously insisted Mexico would fund. But with Mexico City flatly rejecting Trump’s demands to pay for the $25 billion project, and Congress unwilling pay for it the White House wants, the president is looking for other bill payers.

The Pentagon, of course, even with its $700 billion budget, doesn’t have the ability to shift billions around without the approval of Congress, and it would be hard to imagine many lawmakers willing to siphon money from badly needed modernization of procurement plans — which produce jobs in home districts — in order to fund a border wall.

If there is a deployment of National Guard or active duty troops along the border, the move would likely mirror the deployment of hundreds of troops, ground and air defense radars, and Stryker infantry carriers ordered by President Barack Obama in 2012 to plug holes in border protection.

The mission, known as “Operation Nimbus II,” was run by Joint Task Force — North, a U.S. Army North operation, and Customs and Border Protection. That months-long mission saw Army scouts conducting day and night reconnaissance missions using the Long-Range Advanced Scout Surveillance System, a long-range, multi-sensor system that can identify and geolocate distant targets, and reporting back to Border Patrol agents. The troops did not undertake any police or law enforcement activities, which they are barred from doing by the Posse Comitatus law.

The 2012 deployment also sent air defense soldiers to man the Sentinel radar system and the Avenger Air Defense System, which uses infrared heat-sensing technology to track ground and air movement. The deployments came after border patrol agents complained they were undermanned, and worries were growing over a spate of cross-border flights of ultralight aircraft ferrying drugs across the border. The troops were sent to backstop agents as the federal government rushed to hire and train hundreds more. That operation followed on the 2010 deployment of 1,200 National Guard troops to areas along the Texas and Arizona border areas.

A Pentagon spokesman told me that he did not have any more information about possible deployments of troops to the southern border at this time.