Williams Companies stock dropped more than 6 percent Monday as the completion of its $33 billion merger with Energy Transfer Equity (ETE) came into question. ETE shares ended the day down more than 1 percent.
On Friday, a Delaware court ruling said ETE has the right to terminate the merger agreement. Williams Companies, which wants to complete the deal, is expected to appeal the court's decision.
"If ETE attempts to terminate the Merger Agreement, Williams will take appropriate actions to enforce its rights under the Merger Agreement and deliver its benefits to Williams' stockholders," Williams said in a statement.
ETE did not immediately respond to CNBC's request for comment.
Williams Companies shares are down 65 percent over the past 12 months.
Williams Companies 12-month performance:
— CNBC's David Faber contributed to this report.