Homeland Security Secretary Kirstjen Nielsen made the announcement at the White House on Wednesday.
In the original Washington Post article (which was changed without explanation or an editor's note), Alex Mensing, one of the organizers, said the caravan was "a mass nonviolent collective action" that was organized to "raise the political cost of repression" by immigration law enforcement in the us and Mexico. But over the past 12 years, presidents have twice sent National Guard troops to the border to bolster security and assist with surveillance and other support.
Constructing a "big, handsome wall" along the Mexican border was a signature campaign promise for Mr Trump, but so far the plan to erect a new physical barrier has been thwarted by lawmakers and appears to have stalled.
The president had earlier Wednesday tweeted pledging "strong action today", a day after he said he wants to use the military to secure the US-Mexico border until his "big, handsome wall" is erected.
Earlier, Trump told reporters that the Mexican border was very unprotected by the United States laws.
"We have very bad laws for our border, and we are going to be doing some things - I've been speaking with General Mattis - we're going to be doing things militarily", he said.
In 2011, the head of Arizona's National Guard told the Washington Post that his soldiers primarily served as "eyes and ears" at the border.
Trump spoke about the "caravan" at a news briefing at the White House on Tuesday and said he wanted Mexico to prevent people in it from crossing into the US.
"We need to have a wall that's about 700 to 800 miles", he said at a White House meeting, with Defense Secretary Jim Mattis at his side. In 2010, former President Barack Obama dispatched 1,200 National Guard members, followed in 2014 by former Texas Gov. Rick Perry, who mobilized the National Guard to help secure the border.
Trump asserted on Tuesday that in the days since he began to rant about the controversy much of the caravan has been broken up. "But the law is the law and that's what we are enforcing", said Port Director Carlos Rodriguez, who has been with the enforcement agency for 20 years. But the guard members had no authority to pursue, or detain, immigrants attempting to cross the border, that remained the job of U.S. Customs and Border Protection agents.
Elmer Gomez, 38, from eastern El Salvador, has been sleeping with his wife and three children aged 7, 13 and 14 on the soccer field under blankets as they wait for temporary transit visas from Mexico to continue to the U.S. border.
Some specific statutes authorize the president to deploy troops within the United States for riot control or relief efforts after natural disasters.
Federal Law states the military cannot enforce the law on USA soil, unless it is approved by Congress. He added that he would be discussing it with his national security team later in the day.
The administration appears to be considering a model similar to a 2006 operation deployed by President George W. Bush.
The $1.3-trillion spending bill, signed into law by Trump last month, only grants $1.6 billion for border security measures, far short of what the administration has sought.
Trump's comments came as the U.S. Department of Justice moved to establish first-ever quotas for immigration judges aimed at speeding up cases and clearing a backlog.