The Missouri Supreme Court on Thursday unanimously blocked new congressional districts backed by President Donald Trump from being used in the November election, instead ordering a statewide vote on whether to uphold or reject the map.

The decision is a rare setback for Republicans in a national redistricting effort that Trump urged GOP-run states to launch last year. Republicans had hoped Missouri's new congressional boundaries would help them win an additional seat and keep their narrow House majority in the midterms.

Missouri Attorney General Catherine Hanaway, a Republican, said she would immediately appeal to the U.S. Supreme Court, arguing that the ruling "has thrust our State into a full-fledged Constitutional crisis." Further details of the ruling or the districts in question were not provided in the initial report.