CORRECTED - US OKs Metlife buy of residential mortgage assets

(Corrects second paragraph to make clear that acquisition includes assets needed to service the mortgages, and not the mortgages themselves)

WASHINGTON, Aug 21 (Reuters) - U.S. antitrust authorities have given approval for a unit of insurer MetLife Inc (MET.N) to acquire a residential mortgage business from First Tennessee Bank N.A., the Federal Trade Commission said on Thursday.

The deal includes offices, technology and other assets needed to service about $20 billion in first-lien mortgage loans owned by First Tennessee Bank N.A., which is a subsidiary of First Horizon National Corp (FHN.N), MetLife Bank said when the deal was announced in June.

The sale price was not disclosed, but MetLife Bank has agreed to pay book value for the assets purchased.

The antitrust go-ahead was announced in a listing of approved deals that the FTC puts out several times a week. (Reporting by Diane Bartz; Editing by Brian Moss)