Updated July 27, 2017 00:25:32

Photo: Whistleblower Chelsea Manning is the best-known transgendered person to have served in the US army. (Reuters: Elijah Nouvelage)

Donald Trump has said he will not allow transgender individuals to serve in the United States military in any capacity, seemingly unwinding landmark Pentagon policy just 12 months after a transgender ban was lifted.

"After consultation with my Generals and military experts, please be advised that the United States Government will not accept or allow transgender individuals to serve in any capacity in the US Military," President Trump wrote on Twitter.

Up until five years ago, the US military still banned gay troops from openly discussing their sexuality under a "don't ask, don't tell" policy.

But in June 2016, after years of developments to open up the doors to women and the gay community, the Pentagon announced that transgender personnel would no longer be barred from serving openly in the US military, in what was considered a major milestone, despite criticisms.

Under last year's policy, the Pentagon said it would cover medical expenses related to being transgender, including gender reassignment surgeries when they are deemed "medically necessary".

However, Mr Trump's latest tweets say that the US military can no longer afford to be "burdened" by the medical costs and disruption of transgender individuals.

"Our military must be focused on decisive and overwhelming victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail. Thank you," Mr Trump wrote in a follow-up tweet.

The US military has about 1.3 million service members.

According to a RAND study, about 2,500 of these active-duty service members are transgender, as well as about 1,500 out of approximately 825,000 reserve troops.

It is unclear what will happen to transgender individuals serving in the US military who have openly come out since the ban was lifted last year.

The Pentagon shortly after released a statement saying that all questions on Mr Trump's transgender ban should be referred to the White House.

As soon as Mr Trump made his announcement, the American Civil Liberties Union called for transgender service members to contact its lawyers for help.

"Thousands of trans service-members on the front lines deserve better from their commander in chief, @realDonaldTrump. Contact the ACLU," the group said on Twitter.

Whistle-blower Chelsea Manning is perhaps the best-known transgendered person to have served in the US military.

ABC/Reuters

Topics: army, world-politics, donald-trump, gays-and-lesbians, united-states

First posted July 26, 2017 23:39:24