Staples revealed Monday that the Federal Trade Commission has rejected its offer to revise its $6.3 billion acquisition of Office Depot, casting further doubt over whether the merger between the two largest office supply chains will ever reach its completion.

"The FTC rejected the company's offer without making a counteroffer," Staples said in a statement. 

The deal has been under the scrutiny of federal regulators ever since it was announced, and two weeks ago the FTC filed an administrative complaint challenging the deal. They argue that the merger of these two chains would give the resulting company too much pricing power in its segment of the market proving office supplies directly to businesses, according to the United Press International.

Initially, in order to allay these fears, the company offered to sell commercial contracts worth $500 million. This amount was increased to $1.25 billion in the most recent offer, but it was rejected as well.

Now Staples is looking to pursue the transaction through litigation, according to The Seattle Times.

"The company is confident in its legal position and looks forward to a full and impartial judicial review of the matter," Staples said in a statement.

Shares of both companies didn't change too much despite the setback. Staples shares fell 1 percent to $9.30 in pre-market trading, while Office Depot were flat at $5.41.