Trans European travelers warned by their countries about US travel amid Trump 'two-sexes' order

"When applying for an ESTA or visa to the United States, there are two gender designations to choose from: male or female," the Danish travel advisory said on its website.

The Electronic System for Travel Authorization (ESTA) is the system that screens passengers before they travel to the U.S. under the Visa Waiver Program.

"If you have the gender designation X in your passport, or you have changed your gender, it is recommended that you contact the U.S. Embassy prior to travel for guidance on how to proceed," the website reads.

Finland also updated its website in recent weeks.

The new advisory does not explicitly mention the Trump administration, but it comes as the U.S. State Department aligned its policies with President Trump's goals of only having "male" or "female" on American passports.

"For example, transgender travelers may encounter difficulties entering certain countries if they present a passport with a name and photo that no longer corresponds to their gender identity," their information for LGBTQ travelers states.

Trump signed the executive order titled "Defending Women from Gender Ideology Extremism and Restoring Biological Truth to the Federal Government" in one of his first actions in January. It reiterates that the administration recognizes there are only two sexes, male and female, defined strictly by biological characteristics determined at conception. It mandates that federal agencies enforce this binary understanding of sex across the federal government, including in healthcare, education and military service.