Donald Trump said on Wednesday that he will reinstate a ban on transgender people from serving “in any capacity” in the US armed forces.

Trump tweeted that he will reverse a policy which was approved by the Defense Department last year under President Barack Obama, but which was still under final review.

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.

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.

Defense Secretary James Mattis announced last month that he was delaying enactment of the plan.

Trump did not explain his invocation either of “tremendous medical costs” or of “disruption”.

White House Press Secretary Sarah Huckabee Sanders could not say what would happen to active transgender military members. Instead, she asserted that the White House and the Defense Department would work together “as implementation takes place and is done so lawfully”.

Sanders also cited issues with health costs and “military readiness and unit cohesion”, insisting that Trump’s announcement was a “military decision” and “not meant to be anything more than” that. She said the decision was made with Trump’s national security team.

A 2016 RAND study for the Defense Department concluded that transgender service has a “minimal impact” on readiness and health care costs.

The study put the number of transgender people in the military between 1,320 and 6,630, estimating the possibility of 30 to 140 new hormone treatments a year in the military, with 25 to 130 gender transition-related surgeries among active service members. The cost could range from $2.4 million and $8.4 million, an “exceedingly small proportion” — 0.0004% to 0.0017% of the $49.3 billion health care expenditure in the military.

Trump had proclaimed in his 2016 campaignm that he would be a strong defender of the LGBT community, making a better president for than than his opponent Hillary Clinton: “I will tell you who the better friend is and some day I believe that will be proven out big league.”

Report: Trump’s Transgender Tweet Was to Save Spending Bill, Including “The Wall”

Politico claims from multiple sources that Trump struck on Twitter because of fears that the transgender issue would block a House of Representatives spending bill, including money for “The Wall” on the US-Mexican border and increading funding of the military.

The site says GOP legislators told Trump of their concerns that defense hawks wanted a ban on Pentagon-funded sex reassignment operations, a demand resisted by Republican leaders.

Trump quickly responded, going beyond the specific issue of gender-reassignment surgery to declare the ban on military service, even though Defense Secretary James Mattis had refused to change the 2016 policy.

“This is like someone told the White House to light a candle on the table and the WH set the whole table on fire,” a “senior House Republican aide” said in an e-mail. The source said that GOP leaders were not expecting — and had no notice — of Trump’s far-reaching directive.

An administration official was not as concerned, “It’s not the worst thing in the world to have this fight.”