AMENDMENT TO OP CONTRIBUTION AGREEMENT

Exhibit 10.52

AMENDMENT TO

OP CONTRIBUTION AGREEMENT

This AMENDMENT TO OP CONTRIBUTION AGREEMENT (this “Amendment”) is entered into as of December 16, 2010, by and among American Assets Trust, L.P., a Maryland limited partnership (the “Operating Partnership”), American Assets Trust, Inc., a Maryland corporation (the “REIT”), and the contributors whose names appear on Schedule I hereto (each a “Contributor” and, collectively the “Contributors”). The REIT, the Operating Partnership and the Contributors are referred to herein from time to time individually as a “Party” and collectively as the “Parties.” Capitalized terms used herein without definition shall have the meanings assigned to such terms in the Contribution Agreement (as defined below).

RECITALS

WHEREAS, the REIT desires to consolidate the ownership of a portfolio of properties currently owned, directly or indirectly, by the American Assets Entities, pursuant to the Formation Transactions, which relate to the proposed initial public offering (the “IPO”) of the REIT Shares;

WHEREAS, on September 13, 2010, in connection with the Formation Transactions and the IPO, the Parties entered into the Contribution Agreement, pursuant to which the Contributors agreed to contribute to the Operating Partnership, and the Operating Partnership agreed to acquire, all of the Contributors’ interests in the Contributed Entities (the “Contribution Agreement”);

WHEREAS, pursuant to the Contribution Agreement, “Excluded Assets” of the Contributed Entities will be distributed or paid out to the Contributors prior to, or as soon as possible after, the Closing;

WHEREAS, the Parties wish to amend the Contribution Agreement to clarify the method of calculating “Excluded Assets” set forth in Schedule 5.05 of the Contribution Agreement;

WHEREAS, the Parties wish to clarify the definition of “Actual Balance” included in Schedule III to the Contribution Agreement to clarify that consideration payable to the Contributors pursuant to the Contribution Agreement shall not be reduced twice to the extent that certain assumption fees and related expenses and certain prepayment penalties and related expenses relating to Existing Loans are paid by the Contributors, the Contributed Entities or any Subsidiary thereof;

WHEREAS, the Parties wish amend the Contribution Agreement to correct certain clerical errors;

WHEREAS, Section 6.17 of the Contribution Agreement provides that the Contribution Agreement may be amended by appropriate instrument, without the consent of any Contributor, at any time prior to the Closing Date; provided, that no such amendment, modification or supplement may be made that alters the amount or changes the form of the

consideration to be delivered to the Contributors, without the prior written consent of the Contributor adversely affected by such proposed amendment, modification or supplement;

WHEREAS, this Amendment does not adversely affect the amount of or change the form of the consideration to be delivered to any of the Contributors; and

WHEREAS, the Contributors have granted a power of attorney to the REIT authorizing the REIT to enter into this Amendment on their behalf.

NOW, THEREFORE, in consideration of the respective covenants and promises contained herein and for good and valuable consideration, the receipt and adequacy of which is hereby acknowledged, the Parties agree as follows:

1. Excluded Assets. The second sentence of Schedule 5.05 of the Contribution Agreement is hereby deleted and replaced with the following sentence:

““Net Working Capital” means the greater of (a) current assets minus current liabilities of the relevant entity as of a date, chosen by the REIT, within forty five (45) days prior to the date of the preliminary prospectus used in the IPO roadshow or (b) current assets minus current liabilities of the relevant entity as of the Closing Date.”

2. Actual Balance. The following sentence is hereby inserted at the end of the current definition of “Actual Balance” in Schedule III of the Contribution Agreement:

“For the sake of clarity, “Actual Balance” shall not be deemed to include, with respect to any Existing Loan to be assumed, prepaid, repaid or refinanced in connection with the Formation Transactions, assumption fees and related expenses or prepayment penalties and related expenses applicable to such Existing Loan, to the extent such fees and expenses are paid at or prior to the Closing by the Contributors, any Contributed Entity or any Subsidiary thereof (other than payments made by American Assets, Inc. on behalf of American Assets Entities in which American Assets, Inc. does not have a direct or indirect Contributed Interest and for which American Assets, Inc. will be reimbursed by the REIT) and the ultimate effect of inclusion thereof in the definition of “Actual Balance” would be to double-count the amount of such fees and expenses in the calculation of Equity Value and Net Working Capital.”

3. Clerical Errors.

(a) The reference to Schedule 5.03 found in Section 5.05 of the Contribution Agreement is hereby deleted and replaced with a reference to Schedule 5.05.

(b) The reference to Schedule 5.03 found in the definition of “Target Net Working Capital” in Schedule III to the Contribution Agreement is hereby deleted and replaced with a reference to Schedule 5.05.

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(c) The reference to Schedule 5.03 found in the definition of “Excluded Assets” in Schedule III of the Contribution Agreement is hereby deleted and replaced with a reference to Schedule 5.05.

4. Full Force and Effect. Except as explicitly modified or amended pursuant to this Amendment, the Contribution Agreement shall remain unmodified and in full force and effect.

5. Governing Law. This Amendment shall be governed by, and construed in accordance with, the laws of the State of California, regardless of any laws that might otherwise govern under applicable principles of conflicts of laws thereof.

6. Counterparts. This Amendment may be executed in one or more counterparts, each of which is an original, but all of which together constitute one and the same instrument.

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IN WITNESS WHEREOF, the Parties have executed this Amendment to the Contribution Agreement as of the date first above written.

AMERICAN ASSETS TRUST, L.P.,
a Maryland limited partnership
By:		AMERICAN ASSETS TRUST, INC., a Maryland corporation
Its:		General Partner
By:		/s/ ▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Name:		▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Title:		President
AMERICAN ASSETS TRUST, INC.,
a Maryland corporation
By:		/s/ ▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Name:		▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Title:		President
EACH CONTRIBUTOR LISTED ON SCHEDULE I HERETO
By:		AMERICAN ASSETS TRUST, INC., a Maryland corporation
Its:		Attorney-in-Fact
By:		/s/ ▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Name:		▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇▇▇
Title:		President

[Signature Page to Amendment to OP Contribution Agreement]

Schedule I

CONTRIBUTORS

Contributor		Address		Contributed Interest
American Assets, Inc.		See Company’s Files		American Assets Trust Management, LLC Pacific Santa Fe Holdings, L.P.
Bee-Dee Investments, Ltd.		See Company’s Files		ICW Valencia, L.P.
▇▇▇▇▇ ▇▇▇▇▇▇▇		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇▇		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇		See Company’s Files		Winrad Kearny Mesa Business Center
▇▇▇▇▇▇ ▇▇▇▇ Trust		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇▇ ▇▇▇▇		See Company’s Files		Winrad Kearny Mesa Business Center
▇▇▇▇▇▇ ▇▇▇▇ Trust U/D/T March 10, 1983, as amended		See Company’s Files		Pacific American Assets Holdings, LP Carmel Country Plaza, L.P. Pacific Carmel Mountain Holdings, L.P. Pacific National City Holdings, L.P. Pacific Solana Beach Holdings, L.P. Pacific Sorrento Valley Holdings I, L.P. Pacific Sorrento Valley Holdings II, L.P. Mariner’s Point, LLC
ESW LLC		See Company’s Files		EBW Hotel LLC
Gaidebro Holdings, Inc.		See Company’s Files		Pacific National City Holdings, L.P. Pacific Solana Beach Holdings, L.P. Pacific San ▇▇▇▇ Holdings, L.P. Pacific Sorrento Mesa Holdings, L.P. Beach Walk Holdings, LP ICW Valencia, L.P.
▇▇▇▇ ▇▇▇▇▇▇		See Company’s Files		Winrad Kearny Mesa Business Center

Contributor		Address		Contributed Interest
▇▇▇▇▇ ▇▇▇▇ Trust		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇▇		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇▇		See Company’s Files		Pacific American Assets Holdings, LP
Marblank Investments, Inc.		See Company’s Files		Pacific National City Holdings, L.P. Pacific Solana Beach Holdings, L.P. Pacific San ▇▇▇▇ Holdings, L.P. Pacific Sorrento Mesa Holdings, L.P.
▇▇▇▇▇ ▇▇▇▇ Trust		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇▇		See Company’s Files		Winrad Kearny Mesa Business Center
▇▇▇ ▇▇▇▇▇▇▇▇▇▇		See Company’s Files		Pacific American Assets Holdings, LP
▇▇▇▇ ▇▇▇▇▇▇▇		See Company’s Files		Carmel Country Plaza, L.P. Winrad Kearny Mesa Business Center ICW Plaza, L.P., a California limited partnership San Diego Loma Palisades, L.P.
▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇		See Company’s Files		Winrad Kearny Mesa Business Center