The hotel industry is objecting the proposed combination of travel booking sites Expedia and Orbitz, saying that the deal would mean higher prices for vacationers and larger fees for hotel owners.
The American Hotel & Lodging Association says the deal would "severely reduce consumer choice" and hurt many of the trade group's members who are small business owners and franchised properties.
If the merger goes through Expedia and competitor The Priceline Group Inc. will control 95 percent of the online travel agency bookings in the U.S., according to the hotel trade group. Priceline owns sites such as Booking.com and Kayak.
Expedia agreed to buy Orbitz for $1.3 billion in February and Orbitz shareholders approved the sale in May.
The U.S. Department of Justice is still reviewing the deal.