(Bloomberg)—Staples Inc. will have to do more to smooth government opposition to its proposed takeover of Office Depot Inc. after the U.S. rejected its latest attempt to win antitrust approval.

Staples, No. 21 in the B2B E-Commerce 300, which ranks B2B companies by their annual e-commerce sales, said it offered to transfer commercial contracts worth up to $1.25 billion from $500 million previously, according to a statement Monday. Office Depot is No. 42 in the B2B E-Commerce 300.

The Federal Trade Commission’s rejection of that offer raises the stakes for Staples and Office Depot, which have said a drawn-out administrative challenge will kill the deal. The FTC says that the tie-up of the No. 1 and No. 2 office-supply retailers will eliminate competition and raise prices for corporate customers that purchase under contract. 

For more about the FTC’s actions regarding the proposed merger, click here.