A Colorado resident denied a passport for refusing to identify as either male or female on the application form has sued the federal government to try to force the US to join a handful of other countries that allow people to get travel documents without picking a gender.

Lambda Legal announced the lawsuit Monday on behalf of Dana Zzyym (pronounced Zimm) of Fort Collins, Colorado, who was born with ambiguous sex characteristics – referred to as intersex. It names Secretary of State John Kerry as a defendant and claims that requiring people to check a box marked either “M” or “F” is discriminatory and asks people like Zzyym to lie.

Countries including Australia, New Zealand and Nepal allow people to have their gender marked as “X” or “other” rather than male or female on passports. Australia requires people using that option to provide confirmation from a doctor or psychologist.

One of Zzyym’s lawyers, Paul Castillo, said people with such foreign travel documents are permitted to enter the US and he suggested that federal officials also allow an “x” option on its passport applications.

Ashley Garrigus, a spokeswoman for the State Department’s Bureau of Consular Affairs, said the department would not comment on pending litigation.

It’s not clear how many people would want to take advantage of the “x” option. Castillo said an estimated 1.7% of the population is intersex – making them about as common as people with red hair – but some identify as men or women, unlike Zzyym.

Lambda Legal previously joined other groups in pressing the State Department to change its passport policy for transgender people. Since 2010, people who undergo gender reassignment surgery have been able to change the gender on their passports with certification from a doctor. Temporary passports also are granted to people who are going through a gender transition.

Castillo said there is no gender listed on Zzyym’s birth certificate. Zzyym’s parents raised their child as a boy, when Zzyym underwent some medical procedures to change characteristics. Zzyym later served in the US navy as a man before identifying as intersex while working and studying at Colorado State University.

Zzyym grew more aware of gender identity and activism working with the Organisation Intersex International and later unsuccessfully applied for a passport. Zzyym sought one after being invited to participate in the group’s meeting in Mexico City in October 2014, but was unable to go.

“I defended the rights of this country. I believe I should be able to use a few of them,” said the self-described air force brat, who was born in Michigan.

