Secretary of State Marco Rubio, in a memo reviewed by NBC News, said additional guidance would be issued on existing passports containing an “X” sex marker.

The Guardian reports that the U.S. State Department has frozen all applications for passports with “X” sex markers and changes to gender identity on existing passports. The move follows an executive order signed this week by President Donald Trump declaring there are only two “immutable biological classifications” – male and female.

Passport applicants who call the State Department’s National Passport Information Center with questions are being told to wait for new guidance before applying if they can, whic