The proposed merger of daily fantasy sports operators DraftKings and FanDuel appears dead in the water after the US Federal Trade Commission (FTC) filed suit to block the union.

As rumored last week, the FTC filed a complaint on Monday to block the proposed merger of DraftKings and FanDuel based on the FTC’s view that the combined entity would control over 90% of America’s DFS market. The FTC has authorized staff to seek a temporary restraining order and preliminary injunction to forestall the merger ahead of an administrative trial scheduled for November 21.

Tad Lipsky, acting director of the FTC’s Bureau of Competition, said in a statement that the merger “would deprive customers of the substantial benefits of direct competition” between the two DFS giants. Lipsky said the FTC’s filing demonstrated the regulator’s commitment to “the preservation of competitive markets.”

The DFS operators had argued that their dominance of the DFS market had to be seen in context with the overall fantasy market, which includes season-long contests. But the FTC believes DFS players “are unlikely to view season-long contests as a meaningful substitute” for real-money DFS.