Exhibit 99

UBS

UBS Bank USA

C/o UBS Financial Services Inc.

1000 Harbor Blvd./7th Floor

Weehawken, NJ  07086

September 3, 2009

CLEAN DIESEL TECHNOLOGIES, INC.

ATTN: ANN RUPLE

10 MIDDLE STREET  SUITE 1100

BRIDGEPORT CT  06604-4259

Dear Valued Client:

This letter confirms the adjustments made to your Credit Line account:

Account Number: 5V57679

Previous Credit Approval*: $6,500,000.00

Adjusted Credit Approval*: $7,700,000.00

Please contact your Financial Advisor regarding information about your Credit Line or other credit services.

Thank you for choosing UBS Bank USA.

Sincerely,

/s/  Steven M. Stewart

Steven M. Stewart

Senior Vice President

UBS Bank USA