Donald Trump has announced that transgender individuals will not be allowed to serve in "any capacity" in the US military.
In a series of tweets, the president revealed that he had reached the decision after discussions with his generals.
"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," Trump tweeted.
"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."
For many years, transgender people were not permitted to be involved with the US military until June 2016 when it was announced that the ban on transgender people was to be lifted as part of a twelve-month transition period to help those affected.
The lift on the the transgender ban meant that individuals could no "longer be discharged, denied reenlistment, involuntarily separated, or denied continuation of service because of being transgender."
The 2016 RAND study on open serving transgender individuals estimated that there were already around 4,000 serving or reserves in the military.
Reuters reported that the Pentagon has already decided to allow currently-serving transgender troops to stay in military. Other reports have also suggested that Trump's announcement took the Pentagon with little or no communication between the two.
The Williams Institute on Sexual Orientation and Gender Identity Law and Public Policy in 2014 estimated that around 21.4% of all transgender individuals in the US had served in the military at some point.
During the 2016 presidential election campaign, Trump said that "I'm much better for the gays" compared to Hillary Clinton.
After the announcement, a Trump spokesperson told Axios that the decision was heavily politicised, they said: "This forces Democrats in Rust Belt states like Ohio, Michigan and Wisconsin, to take complete ownership of this issue."
Reacting to the announcement, Chelsea Manning, a transgender former US soldier who was jailed for disclosing 750,000 files as part of the Wikileaks, accused the president of cowardice.
She said: "so, biggest baddest most $$ military on earth cries about a few trans people but funds the F-35? sounds like cowardice."
The F-35 fighter plane programme is the most expensive military weapons system in history, with soaring costs and at one stage was behind schedule by seven years.
Chris Barron who heads up 'LGBT for Trump' reacted by saying: "President Trump is committed to defeating the forces of radical Islam that seek the global extermination of LGBT people.
"I defer to the military leaders to determine what policies around the question of trans service best allow them to win the war on radical anti-LGBT Islamic extremism."
The former vice-president Joe Biden was blunt in his words saying: "Every patriotic American who is qualified to serve in our military should be able to serve. Full stop."
Congresswoman Ileana Ros-Lehtinen, a Republican in the Trump state of Florida who has a transgender son said: "No American, no matter their sexual orientation or gender identity, should be prohibited from honour + privilege of serving our nation #LGBT."
Another Republican senator Orrin Hatch of Utah, one of the longest serving senators in US history, broke ranks by proclaiming he was supportive of the transgender community.
Trump appeared to be a supporter of LGBT rights in 2016 when he promised to protect the freedoms and beliefs of those in the LGBT community which were supposedly "threatened" by Hillary Clinton. This has turned out not to be the case.
The news comes almost on the very same day in 1948 that President Harry Truman desegregated the military of the United States.