A pro-family lobbying group listed as a 'hate group' by civil rights activists has been included in the US delegation at key United Nations meetings, rights activists say.
The revelation has fuelled fears that the Trump administration will roll back gay rights.
The Center for Family and Human Rights (C-FAM) was named this week by the US State Department to attend the UN's Commission on the Status of Women, an annual set of high-level meetings on women's equality and empowerment.
C-FAM has been listed as an anti-LGBT hate group by non-profit civil rights group the Southern Poverty Law Center (SPLC) for at least five years, SPLC spokesperson Heidi Beirich said.
"The way you get on our anti-gay hate list is basically if you demonise the gay population," Ms Beirich said. "That's how they ended up on the list."
The move comes as decisions by President Donald Trump's new administration raise fears of a rollback of LGBT rights.
Mr Trump has voiced support for LGBT rights, but his administration has revoked federal guidelines that let transgender students use bathrooms of their choice. Vice-President Mike Pence has expressed staunch opposition to gay rights.
Neither C-FAM nor the State Department responded immediately to requests for comment.
C-FAM's longtime leader Austin Ruse has often been quoted saying he supports the criminalisation of homosexuality, which he calls "harmful to public health and morals", Ms Beirich said.
Articles by Mr Ruse have accused the administration of former President Barack Obama of promoting a "homosexual agenda".
Gay rights made headway under Mr Obama's administration.
Same-sex marriage was legalized in 2015, and Mr Obama also issued regulations prohibiting health insurers from denying coverage based on gender identity, among other measures.
On its website, C-FAM says its mission is "to defend life and family at international institutions".
Ms Beirich said the inclusion of C-FAM "is taking the State Department in a very ugly direction" and failing to address the violence and discrimination faced by LGBT people in some places.
"When you take this anti-gay tone openly, that provides an opening for people to continue those horrible practices," she said.
"We want the State Department to be a beacon of freedom and safety for communities, and this is the opposite of that."