A transgender child's desire to join her school's female running team could be decided by the US Supreme Court after West Virginia on Friday asked the high court to rule on the controversial case.

The court was asked to overturn a lower appeals court decision that freezed West Virginia's 2021 law banning Becky Pepper-Jackson and others like her from competing with other girls because she was born a biological male.

It could lead to the Supreme Court's first-ever intervention in the hot-button issue of trans girls and women in sports.

Backed by the American Civil Liberties Union, Pepper-Jackson, 11 at the time, sued in 2021 to block the West Virginia law so that she could join her school's girls cross-country team.

Her case argued that the state law violates guarantees of equal rights under the US Constitution and the 1972 federal law known as Title IX that prohibits discrimination in schools based on sex.

She lost that suit in the federal district court early this year, the court ruling that the state law did not contradict federal protections because they all linked equal treatment to a person's sex as assigned at birth.

Pepper-Jackson then successfully asked the regional federal appeals court to put a stay, or freeze, on implementation of the law pending her appeal.

On Friday the state, backed by the conservative Alliance Defending Freedom, asked the Supreme Court to overturn the appeals court's stay.

"Biological differences between males and females matter in sports," they argued.

They argued that Pepper-Jackson's case demands setting new definitions based on gender identity rather than biological sex.

That would upend the goal of having clearly separate but equal opportunities for male and female athletes in schools, they said.

Heated political issue

But Pepper-Jackson's attorneys have argued that equal treatment should extend to her gender.

Her case was buttressed by the fact that she had competed "without incident" with her school team over 2021 and 2022 while the new law was appealed, they said.

"Despite regularly finishing near the back of the pack, she has reaped the benefits of school sports: her mother has 'never seen [her] happier'," they said in an appeals court filing.

Denied the ability to continue competing, Pepper-Jackson would incur "irreparable harm," her lawyers argued.

Trans people in sport has become a heated political issue in the United States, with religious conservatives especially fighting against their inclusion on girls teams.

In 2022 a trans woman, Lia Thomas, controversially won the national championship in a university swimming event.

In the Pepper-Jackson case, Supreme Court justices could support or overturn the stay without comment, leaving the case to be argued in full in the appeals court.

But they could also indicate what they feel about the broader issue and whether they would like to have the West Virginia case argued before them for a more lasting ruling.

© Agence France-Presse