SIOUX CITY, Iowa (AP) – The operator of Sioux City’s riverboat casino has turned down a contract offer from its nonprofit partner that holds the gambling license.

The Missouri River Historical Development on Monday approved an extension of its operating agreement with Penn National Gaming Co. through March 2015, and added language that would allow the group to negotiate with other operators on a new land-based casino.

Penn rejected the offer on Tuesday.

The Sioux City Journal  says the move could set up a showdown at Thursday’s meeting of the Iowa Racing and Gaming Commission. The current contract expired in July, and the commission has warned that if a short-term deal isn’t reached by this week, the state may have no other choice but to shut down the riverboat, which has over 300 employees.