Secretary of State Mike Pompeo said Tuesday that a migrant caravan would not be successful in violating the United States' sovereignty.
This process however, has been sharply criticised by advocates, who accuse officials of illegally trying to block immigrants from claiming asylum.
ICE has been talking with contractors to discuss the possible need for additional detention capacity, according to the DHS official.
"Well, it's inconceivable that there are not people of Middle Eastern descent in a crowd of more than 7,000 people advancing toward our border", Pence argued with a shrug.
Another migrant caravan is bound for the USA and is now gathering steam in Central America.
The order would also create new laws disqualifying migrants who cross the border in between ports of entry from claiming asylum, the Times said, quoting people familiar with the plan, although exceptions would be made for people facing torture at home.
Hondurans travelling north as part of a so-called caravan climb onto a truck in Escuintla, Guatemala, on 18 October 2018. "But they could very well be", Trump said.
Saying that the UNHCR at present is concerned by the developing humanitarian situation and the known kidnapping and security risks in areas the caravan may venture into, he told reporters that stabilizing the situation has become urgent.
The number of migrants who unlawfully entered the USA with a family member spiked in September as Trump cast immigration as a crisis.
The additional troops are to provide what one official described as logistical support to the Border Patrol, which is preparing for the arrival of thousands of Central American migrants who are crossing Mexico and aiming for the USA in a huge convoy - many on foot.
The total number of families who arrived at the border during the fiscal year that ended September 30 was 107,212. From there, the migrants walked to Nueva Ocotepeque from where they crossed into Guatemala. Apprehensions at the southwest border sometimes exceeded 1 million a year under President George W. Bush.
Exhausted of waiting and increasingly anxious they might get turned back by Mexican immigration officials, some migrants lowered themselves from the bridge into the river by ropes while others jumped. The timing of the announcement is consistent with the border patrol's past practices. In September, 16,658 people were caught crossing with at least one other relative, up from just under 13,000 in August and 4,200 in September 2017.
Thousands of mainly Honduran migrants heading to the United States - a caravan President Donald Trump has called an "assault on our country" - stopped to rest Tuesday after walking for two days into Mexican territory.
Under current immigration law, for example, all individuals are entitled to certain rights and legal protections while in the custody of the USA government, including illegal aliens. At rallies and on Twitter, Trump has tried to portray the Democrats as pro-illegal immigration, even claiming, with no evidence, that Democrats had organized and paid for the caravan. A Venezuela Information Ministry official declined to comment.