CLIFFS NATURAL RESOURCES INC. SUPPLEMENTAL RETIREMENT BENEFIT PLAN

Exhibit 10(mmm)

CLIFFS NATURAL RESOURCES INC.

SUPPLEMENTAL RETIREMENT BENEFIT PLAN

(as Amended and Restated Effective December 1, 2006)

TABLE OF CONTENTS

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CLIFFS NATURAL RESOURCES INC.

SUPPLEMENTAL RETIREMENT BENEFIT PLAN

(as Amended and Restated Effective December 1, 2006)

WHEREAS, Cliffs Natural Resources Inc (“Cliffs”) and its subsidiary corporations and affiliates have established, or may hereafter establish, one or more qualified retirement plans;

WHEREAS, the qualified retirement plans, pursuant to Sections 401(a) and 415 of the Internal Revenue Code of 1986, as amended, place certain limitations on the amount of contributions that would otherwise be made thereunder for certain participants;

WHEREAS, Cliffs now desires to provide for the contributions which would otherwise have been made for such participants under certain of its qualified retirement plans except for such limitations, in consideration of services performed and to be performed by each such participant for Cliffs and its subsidiaries and affiliates; and

WHEREAS, Cliffs has entered into, and Cliffs and its subsidiary corporations and affiliates may in the future enter into, agreements with certain executives providing for additional service credit and/or other features for purposes of computing retirement benefits, in consideration of services performed and to be performed by such executives for Cliffs and its subsidiaries and affiliates.

NOW, THEREFORE, Cliffs hereby amends and restates and publishes the Supplemental Retirement Benefit Plan heretofore established by it, which shall contain the following terms and conditions:

1. Definitions . A. The following words and phrases when used in this Plan with initial capital letters shall have the following respective meanings, unless the context clearly indicates otherwise. The masculine whenever used in this Plan shall include the feminine.

B. “ Affiliate ” shall mean any partnership or joint venture of which any member of the Controlled Group is a partner or venturer and which shall adopt this Plan pursuant to paragraph 5.

C. “ Beneficiary ” shall mean such person or persons (natural or otherwise) as may be designated by the Participant as his Beneficiary under this Plan. Such a designation may be made, and may be revoked or changed (without the consent of any previously designated Beneficiary), only by an instrument (in form acceptable to Cliffs) signed by the Participant and may be revoked or changed (without the consent of any previously designated Beneficiary), only by an instrument (in form acceptable to Cliffs) signed by the Participant and filed with Cliffs prior to the Participant’s death. In the absence of such a designation and at any other time when there is no existing Beneficiary designated by the Participant to whom payment is to be made pursuant to his designation, his Beneficiary shall be his beneficiary under the Pension Plan. A person designated by a Participant as his Beneficiary who or which ceases to exist shall not be entitled to any part of any payment thereafter to be made to the Participant’s Beneficiary unless the Participant’s designation

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specifically provided to the contrary. If two or more persons designated as a Participant’s Beneficiary are in existence, the amount of any payment to the Beneficiary under this Plan shall be divided equally among such persons unless the Participant’s designation specifically provided to the contrary.

D. “ Code ” shall mean the Internal Revenue Code of 1986, as it has been and may be amended from time to time.

E. “ Code Limitations ” shall mean the limitations imposed by Sections 401(a) and 415 of the Code, or any successor thereto, on the amount of the benefits which may be payable to a Participant from the Pension Plan.

F. “ Controlled Group ” shall mean Cliffs and any corporation in an unbroken chain of corporations beginning with Cliffs, if each of the corporations other than the last corporation in the chain owns or controls, directly or indirectly, stock possessing not less than fifty percent of the total combined voting power of all classes of stock in one of the other corporations.

G. “ Employer(s) ” shall mean Cliffs and any other member of the Controlled Group and any Affiliate which shall adopt this Plan pursuant to paragraph 5.

H. “ Participant ” shall mean each person (i) who is a participant in the Pension Plan on or after December 1, 2006, (ii) who is a senior corporate officer of Cliffs or a full-time salaried employee of an Employer who has a Management Performance Incentive Plan Pay Band E or above, and (iii) who as a result of participation in this Plan is entitled to a Supplemental Benefit under this Plan. Each person who is as a Participant under this Plan shall be notified in writing of such fact by his Employer, which shall also cause a copy of the Plan to be delivered to such person.

I. “ Pension Plan ” shall mean, with respect to any Participant, the defined benefit plan specified on Exhibit A hereto in which he participates.

J. “ Supplemental Agreement ” shall mean, with respect to any Participant, an agreement between the Participant and an Employer, and approved by Cliffs if it is not the Employer, which provides for additional service credit and/or other features for purposes of computing retirement benefits.

K. “ Supplemental Benefit ” or “Supplemental Pension Plan Benefit” shall mean a retirement benefit determined as provided in paragraph 2.

L. “ Supplemental Retirement Benefit Plan ” or “Plan” shall mean this Plan, as the same may hereafter be amended or restated from time to time.

M. “ Termination of Employment ” shall mean the “separation from service” for purposes of Section 409A of the Code of any Participant or former Participant from his Employer, generally including the severance of such employee’s employment relationship with his Employer for any reason, voluntarily or involuntarily, and with or without cause, including without limitation, quit, discharge, retirement, disability, death, failure to return to

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active employment at the end of a leave of absence (including military leave, sick leave, or other bona fide leave of absence) or permanent decrease in service to his Employer to a level that is no more than twenty percent (20%) of its prior level, as described below. For this purpose, whether a separation from service has occurred is determined based on whether it is reasonably anticipated that no further services will be performed by such employee after a certain date or that the level of bona fide services the employee will perform after such date (whether as an employee or as an independent contractor) would permanently decrease to no more than twenty percent (20%) of the average level of bona fide services performed (whether as an employee or an independent contractor) over the immediately preceding thirty-six (36) month period (or the full period of services if the employee has been providing services for less than thirty-six (36) months). For purposes of this definition, the term “Employer” shall mean the Employer of the Participant and any other entity that is treated as a single employer with such Employer under Section 414(b) and (c) of the Code, provided that in such Code Sections “50%” shall be used wherever “80%” appears. The preceding rule shall only apply during the periods any such corporation, business organization or member would be so considered under Section 414(b) or 414(c) of the Code. The transfer of an employee from the Employer for whom he provides services to any entity that is an Employer within the meaning of the preceding two sentences (or vice versa) shall not constitute a Termination of Employment for purposes of this Plan.

2. Determination of the Supplemental Pension Plan Benefit . Each Participant or Beneficiary of a deceased Participant whose benefits under the Pension Plan payable or accrued on or after January 1, 1995 are reduced (a) due to the Code Limitations, or (b) due to deferrals of compensation by such Participant under the 2005 Cliffs Natural Resources Inc. Voluntary Non-Qualified Deferred Compensation Plan (the “Deferred Compensation Plan”), and each Participant who has entered into a Supplemental Agreement with his Employer (and, where applicable a Beneficiary of a deceased Participant), shall be entitled to a Supplemental Pension Plan Benefit if he should have a Termination of Employment at a time when he is vested in his benefit under the Pension Plan. The amount of the Supplemental Pension Plan Benefit at any time shall be a monthly retirement benefit equal to the difference between:

(i) the amount of the monthly benefit payable or accrued to the Participant or his Beneficiary under the Pension Plan, determined under the Pension Plan as in effect at such time, but calculated without regard to any reduction in the Participant’s compensation pursuant to the Deferred Compensation Plan, and as if the Pension Plan did not contain a provision (including any phase-in or extended wear away provision) implementing the Code Limitations, and after giving effect to the provisions of any Supplemental Agreement, and

(ii) the sum of (X) the amount of the monthly benefit in fact payable or accrued to the Participant or his Beneficiary under the Pension Plan and (Y) the sum of