Sears Holdings Corp sent an open letter on Thursday to independent Web operators affiliated with online retailer Amazon.com inviting them to join its network, becoming the second major U.S. store chain to go after key partners of the Web retailer in recent weeks.

Amazon last week said it may cut ties with its 10,000 California-based affiliates over new tax collection efforts being proposed by California.

The affiliates have found themselves in the middle of an escalating battle between Amazon and several U.S. states, which argue that Amazon must collect sales tax when its affiliates operate in their state.

The affiliates are paid a fee when they drive traffic to Amazon that yields a sale.

Amazon did not immediately respond to a request for comment.

U.S. bookstore chain Barnes & Noble Inc similarly approached Amazon's network affiliates last month, offering to collect and remit taxes due on Barnes & Noble Web sales on their behalf.

Sears said its affiliate network includes 6,500 partners.

(Reporting by Phil Wahba; Editing by Richard Chang)

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