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X UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( D ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 or TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( D ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to AMERICAN ASSETS TRUST , INC . ( Exact Name of Registrant as Specified in its Charter ) Commission file number : 001-35030 AMERICAN ASSETS TRUST AMERICAN ASSETS TRUST , L.P. ( Exact Name of Registrant as Specified in its Charter ) Commission file number : 33-202342-01 Maryland ( American Assets Trust , Inc. ) Maryland ( American Assets Trust , L.P. ) ( State or other jurisdiction of incorporation or organization ) Registrant American Assets Trust , Inc. American Assets Trust , L.P. 11455 El Camino Real , Suite 200 San Diego , California 92130 ( Address of Principal Executive Offices and Zip Code ) 27-3338708 ( American Assets Trust , Inc. ) 27-3338894 ( American Assets Trust , L.P. ) ( IRS Employer Identification No. ) ( 858 ) 350-2600 ( Registrant's Telephone Number , Including Area Code ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of Each Class Common Stock , $ .01 par value per share None American Assets Trust , Inc. American Assets Trust , L.P. Trading Symbol AAT None Securities registered pursuant to Section 12 ( g ) of the Act : Name Of Each Exchange On Which Registered New York Stock Exchange None None None