However, ABC News has learned that the Department of Homeland Security (DHS) had made an initial request to the Pentagon "to hold" migrants seized along the border in tent structures, according to a US official.
Pentagon officials declined a preliminary Trump administration request for the USA military to build facilities to house detained migrants as part of its new mission on the Mexican border, USA officials said.
The service personnel will continue installing barbed-wire fences, building barriers with vehicles and housing for extra US Customs and Border Protection personnel sent to the border.
Trump stirred controversy last Thursday when he told reporters at the White House that if incoming migrants hurl rocks at the troops, they would be met with fire.More news: Krunal Pandya, Khaleel Ahmed handed maiden T20I cap
USA troops, along with Customs and Border Protection officers, have been working to secure sections of the Texas-Mexico border, in part by laying down barbed-wire fencing, as new photos show.
"We're going to have tents".
"Our military will not receive combat pay or hostile-fire pay as they are not deploying to a combat area, nor are they expected to be subject to hostile fire", he said, adding that they will be eligible for a separation allowance.
Trump did not rule out that the final number of soldiers deployed will reach 15,000.More news: Prince Charles arrives in Ghana today
The cost of mobilizing all those troops is estimated to be around $220 million.
According to Pentagon sources on Monday, some 4,600 soldiers have already been mobilised and were stationed in California, Arizona and Texas, and the goal was to mobilise an additional 600 soldiers, reports Efe news.
Trump said last week he plans to build tents to house migrants, who would be held in those facilities while the US government weighs their asylum request.
However, Trump's effort has been embraced by Republicans running in the elections, in which illegal immigration is a top issue. During the walk from the Guatemalan-Mexican border to the Mexican region of Tapachula, police set up road blocks twice with hundreds of riot-control equipped officers, but they were lifted before the migrants got there.More news: IL sees jump in turnout for early voting
Trump's push to send the military to the border comes ahead of Tuesday's mid-term congressional elections and has triggered sharp reactions, with critics calling it a political stunt that misuses USA military resources. Their mission is to keep caravans of Central Americans out.