The Federal Trade Commission, along with the Offices of the Attorneys General in the State of California and the District of Columbia, will file a complaint to block the merger of the two largest daily fantasy sports sites, DraftKings and FanDuel, according to a statement released by the FTC today.

The complaint seeks a “preliminary injunction” on the deal and alleges “that the combined firm would control more than 90 percent of the U.S. market for paid daily fantasy sports contests,” creating what the statement called a “near monopoly.”

A joint statement from DraftKings and FanDuel read:

Today, the Federal Trade Commission (FTC) announced it will attempt to block the proposed merger between DraftKings and FanDuel.

We are disappointed by this decision and continue to believe that a merger is in the best interests of our players, our companies, our employees and the fantasy sports industry. We are considering all our options at this time.

As we work together to determine our next steps, we would like to thank DraftKings and FanDuel players, partners and employees for their patience, support and continued loyalty.

The move to block the merger wasn’t a complete shock; anti-trust conflicts had been a concern when the companies announced the plan last November.