Transgender recruits will be allowed to enlist in the military beginning January 1, the Pentagon said on Monday, as President Donald Trump's ordered ban suffered another legal setback.

The new policy reflects the difficult hurdles the federal government would have to cross to enforce Mr Trump's demand earlier this year to bar transgender individuals from the military.

Two federal courts already have ruled against the ban and on Monday a federal court judge denied a government request to set aside the January start date for enlistment.

In October, US District Judge Colleen Kollar-Kotelly barred the Trump administration from proceeding with its plan to exclude transgender people from military service. Part of the effect of the ruling was that the military would be required to allow transgender people to enlist beginning Jan. 1.

The government had asked Kollar-Kotelly to put the Jan. 1 date on hold while they appealed her full ruling but she declined Monday, reaffirming the Jan. 1 start date.