The Pentagon said on Friday that it expected to send about 300 additional troops to the border with Mexico including roughly 100 cooks who would hand out meals, breaking with past policy to avoid troops coming in contact with migrants.
The move is the latest sign of a growing US military support role for President Donald Trump's politically charged immigration policies.
Earlier this month, Trump said he would have to mobilize more of the military at the US border with Mexico after listening to stories about migrants crossing the border from people attending a Republican fundraiser.
The Pentagon has previously said there were no plans for US forces to interact with migrants as they support border agents dealing with illegal immigration.
In addition to the cooks, the Pentagon is expected to send 160 drivers and 20 lawyers, Pentagon spokesman Charlie Summers said.
"We will have some of our troops handing out meals, therefore would come in contact with migrants," Summers said. He said it was an "amendment to the current policy."
There are currently about 5,000 active-duty and National Guard troops near the border, though that number fluctuates.
There has been increasing concern about the military playing a growing role on the border with Mexico.
The Posse Comitatus Act, a federal law on the books since the 1870s, restricts using the US Army and other main branches of the military for civilian law enforcement on US soil, unless specifically authorized by Congress.
But the military can provide support services to law enforcement and has done so on occasion since the 1980s.
Earlier this month six Mexican military personnel questioned two US Army soldiers near Clint, Texas. A US military investigation found the American soldiers were in US territory during the incident, while the Mexican personnel believed they were south of the border.
Trump has made immigration a signature issue of his presidency and of his re-election campaign. He declared a national emergency over the issue earlier this year in an effort to redirect funding from Congress to build a wall along the US southern border.
On Wednesday, Trump reiterated threats to close part of the US-Mexico border if Mexico doesn't block what described as a new caravan of migrants headed north.