A federal lawsuit threatens to derail a portion of the $1 billion overhaul of Denver's National Western Stock Show complex.
Colorado Public Radio reports Denver Rock Island Railroad is accusing the city of threatening to unlawfully move the rail lines by eminent domain.
The railroad filed the suit last week in Denver's U.S. District Court after negotiations with the city broke down.
Attorneys for the railroad couldn't explain why the city cut off negotiations.
Denver spokeswoman Jenna Espinoza-Garcia would not comment on the negotiations or the lawsuit.
At issue is about four miles of rail on the western edge of the stock show complex that has been in use for more than a century. The city was in negotiations with the railroad to move that track to create an open space at the South Platte riverfront.