President Donald Trump signed an executive order on Monday directing defence secretary Pete Hegseth to revise the Pentagon’s policy on transgender troops, likely setting in motion a future ban on their military service.

He also ordered troops to be reinstated who had left voluntarily or been booted for refusing Covid-19 vaccines, outlined new rollbacks in diversity programmes and provided for the deployment of a space-based missile defence shield for the US — all on Hegseth ‘s first day.

Trump and Hegseth had described parts of the anticipated orders throughout the day, but the exact language did not drop until late on Monday.

A transgender ban had been widely expected, and Trump’s order largely sets the stage for a future ban — but directs Hegseth to come up with how that would be implemented in policy.

In his order, Trump claimed that service by troops who identify as a gender other than their biological one “conflicts with a soldier’s commitment to an honourable, truthful, and disciplined lifestyle, even in one’s personal life” and is harmful to military readiness, requiring a revised policy to address the matter.

Trump had tried to ban transgender troops during his first term, but it was tangled up in the courts for years before being overturned by then-President Joe Biden shortly after he took office.

Two groups, Lambda Legal and Human Rights Campaign, which represented transgender troops the first time, vowed to fight again.

“We have been here before and seven years ago were able to successfully block the earlier administration’s effort,” Lambda Legal attorney Sasha Buchert said. “Not only is such a move cruel, it compromises the safety and security of our country and is particularly dangerous and wrong. As we promised then, so do we now: we will sue.”

During his first presidency, Trump established US Space Command and the US Space Force, which just marked its fifth birthday. Space continues to be a priority for the President, who has now directed the Pentagon to begin to develop the capability to shoot down missiles from space. For years, the US has cautioned that China, Russia and others were weaponising space.