Washington DC - President Donald Trump signed an executive order banning trans people from serving in the military as his crackdown on LGBTQ+ rights continued apace.

In a series of orders related to the military that Trump told reporters he had signed on Air Force One, the Republican also reinstated service members dismissed for refusing to take the Covid vaccine and extended a wider government crackdown on diversity programs to the armed forces.

"To ensure that we have the most lethal fighting force in the world, we will get transgender ideology the hell out of our military," Trump told a Republican congressional retreat earlier in Miami.

A White House official with him said the order involved "eliminating gender radicalism in the military."

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The order, published on the White House website, calls "adoption of a gender identity inconsistent with an individual's sex conflicts with a soldier’s commitment to an honorable, truthful, and disciplined lifestyle."

Trump's orders came at the start of his second week back in the White House and on the day a welcome ceremony was held at the Pentagon for his new defense secretary, military veteran and former Fox News host Pete Hegseth, who has 60 days to implement the order.

"Thank you for your leadership, Mr. President. We will execute!" said Hegseth, who was confirmed last week despite concerns over his inexperience, as well as numerous allegations of heavy drinking, domestic violence, and sexual assault.

Trans Americans have faced a roller coaster of changing policies on military service in recent years, with Democratic administrations seeking to permit them to serve openly while Trump has repeatedly pushed to keep them out of the ranks.

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The US military lifted a ban on transgender troops serving in the armed forces in 2016, during Democrat Barack Obama's second term as president.

Under that policy, trans troops already serving were permitted to do so openly, and trans recruits were set to start being accepted by July 1, 2017. But the first Trump administration postponed that date to 2018 before deciding to reverse the policy entirely, sparking criticism from rights groups.

Trump claimed without any evidence that transgender service members were disruptive, expensive, and eroded military readiness and camaraderie among troops.

Biden moved to reverse the restrictions just days after he took office in 2021, saying all Americans qualified to serve should be able to do so.

While the number of trans troops in the American military is fairly small – with estimates of some 15,000 out of more than two million uniformed service members – their dismissal would reduce US forces at a time when the country is already facing difficulties recruiting new personnel.

SPARTA, a transgender military advocacy organization, told journalist Erin Reed that a quick ban would mean "leaving critical gaps in skill sets, experience, and leadership positions that you're just not going to be able to fill with equivalent people anytime soon, especially given the shortfalls in recruiting."

Reed also cited a trans officer, who said: "Every trans service member that I have observed performing their job excels at their job, and that's because we have to… Every trans sailor, every trans soldier, every trans Marine, and airman that I have known has excelled at their job."