The defense officials described the force DHS requested as something that would only be used if CPB personnel were overwhelmed by the situation on the border.
Secretary of Defense Jim Mattis is sending up to 5,200 troops to the border to defend it from the onslaught of migrants trying to cross into the country.
The supposed request was made at the time when a migrant caravan of mostly Central American asylum-seekers are heading to the U.S. in the hope to cross into the country.
A Pentagon spokesman said Monday that the laying of concertina wire was in line with the mission to help CBP "plug gaps" at ports of entry along the border. "We have a problem with illegal immigration and the problem is that the Democrats will not allow us to change the dumbest laws in the history of the world on immigration". "But we're going to arrest those people quickly and for a long time", he told reporters.
Federal authorities have awarded a $145 million contract to a Texas company to build 6 miles of wall along the U.S. -Mexico border in the Rio Grande Valley.
Indeed, these four caravans now are traveling inside Mexico, totaling some 12,000 Central American migrants, as a separate Fox News report indicated on Sunday and as other outlets have noted.
Manning said only military police would carry weapons and stressed that there were no plans for USA troops to come in contact with protesters or migrants.
Some 1,100 of the troops are in California, another 1,100 in Arizona and 2,600 in Texas on the eve of crucial midterm elections that will determine whether Trump's Republicans keep their hold on power in Congress.
The Pentagon faced questions Monday as to why it selected thousands of active-duty forces to deploy to the border instead of sending additional National Guard.
Manning also clarified that Military Police (MP's) will be the only active duty forces to be armed during the operation.
Asked about the cost of the operation, Manning said it had yet to be determined by the Pentagon's financial services.