Minera Andes 6-K Report of Foreign Issuer Dated March 2, 2009

Exhibit 99.6

April 26, 2007

Messrs.

MINERA ANDES INC.

MINERA ANDES S.A.

111 East Magnesium Rd., Suite A

Spokane, WA

Attention : Allen Ambrose

Facsimile No. (509) 921-7325

MINERA SANTA CRUZ S.A.

Leandro N. Alem Avenue 712, Suite 5A

Capital Federal, Argentina

Attention: Gonzalo Freyre

Facsimile No. (54-ll) 4315-7900

Dear Sirs:

We refer to the letter agreement dated January 5, 2007, as amended, among Hochschild Mining (Argentina) Corporation, formerly known as Lorenzon Limited (“Lorenzon”), Minera Andes Inc., Minera Andes S.A. and Minera Santa Cruz S.A. and the letter agreements dated January 25, 2007 and February 28, 2007, each as amended, among the same parties (collectively, the “Letter Agreements”), each relating to advances of the Lorenzon/MSC PFL, the Lorenzon/MAI PFL, and the MAI/MSC PFL (as such terms are defined in the Letter Agreements).

This will confirm our agreement as follows:

1.

The Letter Agreements are amended by (a) deleting the date “April 30, 2007” in paragraph 2 of each of the Letter Agreements and replacing such date with “June 30, 2007 and (b) deleting the date “May 1, 2007” in each place it appears in paragraph 2 of each of the Letter Agreements and replacing such date with “July 1, 2007.”

2.

As amended hereby, the Letter Agreements remain in full force and effect.

If the foregoing correctly reflects our agreement, please sign a copy of this letter and return it to us.

Very truly yours.

HOCHSCHILD MINING (ARGENTINA)

CORPORATION

By:   /s/  Miguel Aramburú

Name:  Miguel Aramburú

ACCEPTED AND AGREED:

MINERA ANDES INC.

By:      /s/ Allen V. Ambrose     

Name:

Allen V. Ambrose

Date:

May 1, 2007

MINERA ANDES S.A

By:_____________________

Name:

Date:

MINERA SANTA CRUZ S.A.

By:____________________

Name:

Date:

2

ACCEPTED AND AGREED:

MINERA ANDES INC.

By:      /s/ Allen V. Ambrose      

Name:

Allen V. Ambrose

Date:

May 1, 2007

MINERA ANDES S.A

By:    /s/ Jorge A. Vargas             

Name:

Jorge A. Vargas

Date:

27-04-07

MINERA SANTA CRUZ S.A.

By:______________________

Name:

Date:

ACCEPTED AND AGREED:

MINERA ANDES INC.

By:_____________________

Name:

Date:

MINERA ANDES S.A

By:_____________________

Name:

Date:

MINERA SANTA CRUZ S.A.

By:    /s/ Gonzalo Freyre        

Name: Gonzalo Freyre

Date: 27-04-07

2