President Donald Trump took to twitter on Wednesday to announce that he would ban transgender people from serving in the US military.                                                   

"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 U.S. Military," the President said in a series of tweets. "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."                               

The announcement came as a surprise since Trump vowed to fight for lesbians, gays, bisexuals and transgender people while running as a presidential candidate last year, according to Reuters.

It drew condemnation from rights groups and some lawmakers in both parties as discrimination with purely political motives but was praised by conservative activists and some Republicans.

Trump spokeswoman Sarah Sanders said the administration has not yet decided whether transgender service members already in the military would be immediately thrown out, saying the White House and Pentagon would have to work that out.

The decision reverses Democratic former President Barack Obama's policy and halts years of efforts to eliminate barriers to military service based on sexual orientation or gender identity.

"This was about military readiness," Sanders told a briefing. "This was about unit cohesion. This was about resources within the military, and nothing more."

Critics said the health costs of caring for transgender service members were a tiny portion of the military's healthcare budget and that Trump's policy change was based on prejudice.

How much does transgender troops cost?                              

A 2016 RAND Corporation study, which was commissioned by the Defense Department, found that expanding medical coverage to transgender members would cost between 2.4 million to 8.4 million US dollars, with an average median cost increase of 5.4 million dollars annually. That median cost would amount to a health-care spending increase of 0.22 dollars per service member per month, according to RAND.

Sanders said Trump had "extensive discussions with his national security team" and Defense Secretary Jim Mattis was informed after the president made the decision on Tuesday.         

The Pentagon referred questions about Trump's decision to the White House.