Mr. Trump has spoken before about launching a military operation to police the border, only to have his aides walk back the remarks amid a backlash from members of his administration and officials in Mexico.
Last February, he called his immigration crackdown “a military operation,” prompting Rex W. Tillerson, then the secretary of state, and John F. Kelly, then the homeland security secretary, who were visiting Mexico at the time, to push back vigorously. They told their Mexican counterparts and reporters that the American president did not, in fact, plan to use the military to hunt down and deport undocumented immigrants. The White House later insisted that Mr. Trump had meant the word “military” only as an adjective.
On Tuesday, though, the president appeared convinced that American troops were needed.
“We are preparing for the military to secure our border between Mexico and the United States,” he said during a news conference with the Baltic leaders, adding that he would be meeting with Mr. Mattis and other officials on the matter later in the day. “I think it’s something we have to do.”
Mr. Trump’s comments on Tuesday came after he kicked off his third consecutive day of tweeting about America’s “weak” border laws and called on Congress to act on legislation to toughen immigration laws. The push comes as Mr. Trump has complained with increasing urgency about a large group of migrants from Honduras that has been traveling through Mexico.
The caravan has been a popular topic on Fox News — the president’s favorite news network — and his aides have argued that weak immigration policies are luring the migrants from Central America to the United States.
“The big Caravan of People from Honduras, now coming across Mexico and heading to our ‘Weak Laws’ Border, had better be stopped before it gets there,” he tweeted on Tuesday. “Cash cow NAFTA is in play, as is foreign aid to Honduras and the countries that allow this to happen. Congress MUST ACT NOW!
Mr. Trump’s Twitter tirade on immigration policy started Sunday with threats to and, since then, he has consistently threatened to pull out of the North American Free Trade Agreement, known as Nafta. On Tuesday, Mr. Trump said Nafta “is in play,” and repeated his contention that Nafta was a “cash cow” for other nations.
The president’s tweets do not always lead to a new policy, but on Monday afternoon the White House announced Mr. Trump’s new push for legislation to make it more difficult to enter and stay in the United States.
A group called Pueblo Sin Fronteras organized the caravan that has prompted the president’s complaints, which consists of about 1,200 people — including infants, the elderly and people facing violence in their homelands.
Late Monday, Mexican immigration officials started to negotiate with the caravan’s organizers. And Mexican authorities have agreed to provide humanitarian visas to the migrants so that they can stay in Mexico legally, a representative from Pueblo Sin Fronteras said.
On Tuesday, Mr. Trump claimed credit for having persuaded Mexican officials to break up the caravan.