Trump administration has not sent directive but is calling for ban on new recruits and seeks to give defense secretary power to remove those currently serving

New transgender recruits to the US military would be banned and the US defense secretary would have the power to remove those currently serving, under the terms of a new memo from the White House described to reporters.

The Trump administration has not yet sent the directive, which takes the form of a two-and-a-half page memo, to military leaders. But its outline calls for the Pentagon to implement the new ban in six months.

The memo, which was described to reporter for the Wall Street Journal and confirmed to Reuters, would give the defense secretary, James Mattis, the power to decide whether current service members should be removed based on their ability to “deploy” – meaning serve in a war zone, participate in exercises or live for months on a ship. New recruits would be banned and the Pentagon instructed to stop covering transition-related medical care through its insurance programs.

Reports of the memo come one month after Donald Trump appeared to blindside top military officials by announcing that the US military “will not accept or allow … transgender individuals to serve in any capacity”.

After Trump’s announcement, which came in a series of three tweets, Pentagon leaders said they would not alter the current policy, which allows transgender individuals already in the military to serve openly, without formal instruction from the White House.

Backlash to Trump’s 26 July announcement was swift and bipartisan. Trans service members and their advocates declared themselves “ready to fight” a new ban in court, while Republicans such as senators Orrin Hatch and John McCain called for Trump to leave the current policy alone.

“There is no reason to force service members who are able to fight, train and deploy to leave the military – regardless of their gender identity,” McCain said.

The military’s top brass developed the current policy under the instructions of the Obama administration. A plan permitting the military to recruit transgender individuals was placed on hold for six months in June. The accumulated evidence showed that allowing trans people to serve and receive medical treatment related to their transition would not disrupt military preparedness.

A 2016 study by the Rand Corporation and commissioned by Obama’s defense secretary found that between 1,300 and 6,600 trans people were already serving in the military before the ban on open service was lifted, and that only a few dozen individuals each year might undergo transition surgery that would prevent them from being able to be deployed.

Those opposed to transgender service argued the Obama-era policy would weaken military readiness and prove too costly. Trump called the expense of transgender-related medical care “tremendous”, and the congresswoman Vicki Hartzler of Missouri said the cost of covering service members’ transition care was “over a billion dollars”.

Both statements are contradicted by the 2016 Rand study, which estimated that transgender-related healthcare for active duty military would cost $2.4m-$8.4m. In fiscal year 2014, the Pentagon spent $6.27bn on healthcare costs for all active-duty personnel.

Transgender service members who have spoken up against a ban have said expulsion from the military could devastate their lives and careers. Certain types of discharge carry a stigma akin to being a former convict.

“Everybody is hurt. Everybody is scared,” Rudy Akbarian, a 26-year-old trans man and soldier, told reporters in July. “People who enlisted nearly 20 years ago and now 18 or 19 years in, now that’s being taken away and they don’t get to retire?

“This is people’s lives we’re talking about.”