A thousand foreign-born recruits in the U.S. Army may face deportation as the Pentagon reportedly plans to scrap a program that previously promised citizenship to immigrants who were willing to serve.

Citing an undated Pentagon memo prepared for Defense Secretary James Mattis, the Washington Post reports that the Defense Department is mulling the cancellation of the enlistment contracts for immigrant recruits who enlisted through its Military Accessions Vital to National Interest (MAVNI) program.

Under the program, which was launched in 2009, skilled non-citizens or non-legal permanent residents are offered fast-tracked citizenship in exchange for their services.

If the policy is changed, about 1,000 will be vulnerable to deportation as their visas expired as they waited for travel orders.

According to the memo, even the 4,100 troops who are currently serving — most of them already naturalized citizens — are not totally off the hook as they may also face “enhanced screening”.

The Pentagon, however, said it recognizes the “significant legal constraints” of “continuous monitoring” of citizens.

Almost 10,000 MAVNI recruits are now tiered according to “threat levels”, a classification that is reportedly based on certain criteria such as “how thoroughly they have been vetted”, or their level of access to classified information.

Retired Army officer Margaret Stock denounced the document as a “breach of contract made in bad faith”.

“It’s terrible. You trusted the Army, who delayed the process, and now they’re going to cancel your contract and have you deported,” Stock was quoted as saying.

Stock explained that the move would possibly push through as it coincides with the Trump administration’s agenda in ramping up deportations.

She further noted the risks the directive is placing the subjects through.

“It’s okay to investigate someone with a legitimate security threat,” Stock said. “But share a characteristic they don’t like, which is they’re foreigners. They’re going to be treated as second-class citizens for their entire career.”

“I feel it is only right that we honor our contract with them, and that we allow these individuals to continue to live in America once their service has concluded,” Meng wrote in a letter to Trump on Tuesday.

MAVNI was placed under review back in December of 2016 and has been closed indefinitely.