DOVER, Del. — A federal judge in Delaware has indefinitely postponed a scheduled September trial in a lawsuit pitting billionaire coal magnate and West Virginia Democratic gubernatorial nominee James Justice Jr. against a leading U.S. coal exporter.

Attorneys for the Virginia-based Justice companies and Pennsylvania-based Xcoal Energy and Resources told the judge Friday that devastating floods that hit West Virginia in June, prompting Mr. Justice to open his Greenbrier Resort to flood victims, affected document production in the case and delayed completion of depositions. They also noted that Xcoal owner Ernie Thrasher recently became ill and has not been deposed.

The dispute involves a 2011 deal in which Xcoal agreed to buy almost 4 million tons of coal for $560 million. Each side claims the other has failed to live up to its obligations.