Donald Trump has ordered the US Department of Homeland Security (DHS) to add at least 20,000 officers to enforce his deportation policies.

The US president's directive was issued on Friday and forms part of his administration?s plan to incentivise undocumented immigrants to self-deport.

The federal government will fund flights out of the US for undocumented people who choose to leave voluntarily and provide an ?exit bonus?, the executive order stated.

The president?s call to increase staff comes as his administration pursues multiple pathways to force undocumented immigrants to leave the US.

His order on Friday did not specify how the increase in staffing at the DHS would be funded.

Immigrations and Customs Enforcement (ICE), the sub-agency that primarily deals with illegal immigration, currently has more than 21,000 employees.

Of those, it has 6,100 deportation officers and more than 750 enforcement removal assistants, according to the agency?s website.

Trump has long called for local and state law enforcement, as well as the National Guard, to assist with border enforcement.

The order calls on the DHS to supplement its current efforts ?by deputising and contracting with state and local law enforcement officers, former federal officers, officers and personnel within other federal agencies?.

Trump has called for individuals to self-deport, using a government app known as CPB Home. This week, DHS Secretary Kristi Noem announced $1,000 (?751) bonuses and paid travel for people who leave the US voluntarily.

Other deportation methods have been challenged or blocked federal courts, including Trump?s use of the 18th Century Alien Enemies Act to deport Venezuelan migrants his administration accuses of gang activity.

Earlier this month, US District Judge Fernando Rodriguez, a Trump appointee in Texas, found that the administration?s use of the act was ?unlawful.? A second federal judge in New York later reached the same conclusion.

Trump dubbed his self-deportation initiative as ?Project Homecoming?.

He said: ?Illegal aliens who stay in America face punishments, including significant jail time, enormous financial penalties confiscation of all property garnishment of all wages, imprisonment, and incarceration and sudden deportation, in a place, and manner, solely of our discretion.? (BBC)