Adds information on merger's timeline in paragraph 2, stock movement in paragraph 3 and Boeing's comment in paragraph 5

By Dan Catchpole

Dec 3 (Reuters) - A U.S. regulator said on Wednesday it would require Boeing BA.N to divest significant Spirit AeroSystems SPR.N assets to resolve competition concerns about its $8.3 billion acquisition of the company that manufactures major parts of fuselages and wings for aircraft including the Boeing 737.

The Federal Trade Commission's proposed order delays the planned merger, which Boeing had planned to close by the end of the year. There is a 30-day public comment period for the proposed order.

Boeing's share price was down 2.3% in intraday trading.

The commission wants the U.S. planemaker to divest parts of Spirit that supply aerostructures to its European rival Airbus AIR.PA. The three companies have already negotiated Airbus buying parts of Spirit.

The divestment would address the FTC's concerns that the merger would allow Boeing to unfairly control Airbus' supply chain.

“We welcome the U.S. Federal Trade Commission’s approval of our acquisition of Spirit AeroSystems," a Boeing spokesperson said. "While the transaction has not yet fully closed, we are committed to completing the remaining steps necessary to finalize the acquisition. This milestone will further enhance our ability to manufacture safe, high-quality airplanes for our customers and benefit the flying public.”

(Reporting by Bhargav Acharya and Ryan Patrick Jones in Toronto, and Dan Catchpole in Seattle; Editing by Doina Chiacu and David Gregorio)

((dan.catchpole@thomsonreuters.com; 651.231.1623))