(Reuters) - Dollar Tree Inc (>> Dollar Tree, Inc.) said it may need to divest more stores than expected to satisfy antitrust regulators reviewing its planned acquisition of Family Dollar Stores Inc (>> Family Dollar Stores, Inc.).

Dollar Tree has previously said it expects to divest fewer than 300 stores to satisfy the regulators reviewing a deal that would create the No. 1 discount store chain in the United States.

In a filing on Tuesday, the company said the U.S. Federal Trade Commission (FTC) was reviewing more than 500 stores and that it may identify additional stores for review in the future.

"The actual number of divestitures may therefore be above or below 300," Dollar Tree said in the filing.

By acquiring Family Dollar, Dollar Tree will leapfrog rival bidder Dollar General Corp (>> Dollar General Corp.) to become the largest discount retailer in the United States.

Family Dollar shareholders approved Dollar Tree's $8.5 billion cash-and-stock offer last month, scuppering a higher hostile offer from Dollar General. The deal remains subject to FTC approval, expected by the end of March.

Antitrust regulators are scrutinizing the deal over concerns that the merger could result in price hikes at discount stores.

The FTC declined to comment on Tuesday. Family Dollar was not immediately available for comment.

If the deal is approved, Dollar Tree would have more than $18 billion in annual sales and 13,000 stores across the United States and Canada. This total does not take into account possible store divestitures.

Dollar General has about 11,500 stores.

Dollar Tree said the more than 500 stores currently under review represented $75 million to $82 million in pro forma adjusted earnings before interest, tax, depreciation and amortization.

Dollar Tree's shares closed at $74.39 on the Nasdaq on Tuesday. Family Dollar's shares closed at $77.49 on the New York Stock Exchange.

(Reporting by Ramkumar Iyer in Bengaluru; Editing by Joyjeet Das and Robin Paxton)