The Pentagon is readying orders for the deployment of at least 1,000 additional active-duty troops to bolster President Donald Trump’s expanding crackdown on immigration, US officials said on Friday.

They said roughly 500 more soldiers — largely a headquarters unit from the 10th Mountain Division at Fort Drum in New York — will be sent to the southwest border.

About 500 Marines will go to Guantanamo Bay, Cuba, where some of the detained migrants will be held.

The officials, who spoke on condition of anonymity because announcements have not been made, said there have been ongoing discussions about the deployments and the numbers could increase if additional details are worked out.

President Donald Trump listens as Defence Secretary Pete Hegseth speaks in the James Brady Press Briefing Room at the White House (Alex Brandon/AP)

The Pentagon has been scrambling to put in motion Mr Trump’s executive orders signed shortly after he took office on January 20.

The first group of 1,600 active duty troops were deployed to the border last week.

The deployments reflect Mr Trump’s determination to expand the military’s role in his campaign to shut down the border and send detained migrants back to their home countries.

Troops going to the border are expected to help put in place concertina wire barriers and provide needed transportation, intelligence and other support to the Border Patrol. Troops going to Guantanamo could help prepare the facility for an influx of migrants and do other support duties.

Speaking in a television interview on Fox and Friends on Friday, Defence Secretary Pete Hegseth said he believes the US can get “thousands of individuals in tents, secured in places at Guantanamo Bay”.

But he also said there is the possibility that hardened criminals or violent gang members could also be housed there. As a result, he said the Defence Department is preparing detention facilities at Guantanamo “that are basically supermax prisons” to be used to hold them temporarily.

Officials have been saying all week that there are likely to be additional troop deployments to help secure the southern border — potentially rolling out rapidly in the coming days. The eventual total deployed could be as many as 10,000.

Before Mr Trump returned to the White House, there were already about 2,500 Guard and Reserve forces consistently deployed to the border. Officials noted that given the length of the nearly 2,000-mile border with Mexico, it will take additional forces to help put large rolls of concertina wire barriers in place and provide support to the Border Patrol.

President Donald Trump departs the White House on Friday (Jacquelyn Martin/AP)

The roughly 1,100 Army soldiers and 500 Marines ordered to deploy to the border last week have all arrived in El Paso, Texas, and San Diego, and many have already begun work.

Separately, the US military is providing military aircraft for Department of Homeland Security deportation flights for more than 5,000 detained migrants. At least some of those are expected to go to the detention centre at the US military base at Guantanamo Bay.

On Wednesday, the president said his administration planned to send the “worst criminal aliens” to Guantanamo. He ordered the Pentagon to prepare to hold up to 30,000 migrants. He said some of the migrants cannot be trusted to stay in their home countries once they are sent back.

“Some of them are so bad that we don’t even trust the countries to hold them because we don’t want them coming back, so we’re gonna send ’em out to Guantanamo,” Mr Trump said.

This is not the first time migrants have been held at Guantanamo. US authorities have detained migrants intercepted at sea at a facility known as the Migrant Operations Centre, including people from Haiti and Cuba.