San Francisco (CNN Business) Amazon will no longer allow its third-party sellers to use FedEx's ground delivery to ship Prime packages, marking a change that could affect small businesses and pricing for consumers.

The move was highlighted in an email, obtained by The Wall Street Journal , reportedly sent to Amazon's merchant partners on Sunday.

FedEx FDX The email noted performance declines as the reason for the decision to blockGround, according to the Journal. The ban will reportedly take effect this week and last "until the delivery performance of these ship methods improves."

Amazon AMZN As of September, no longer uses FedEx for its own deliveries but it had allowed third-party sellers to use it. Amazon did not release a statement but will still allow merchants to use FedEx's more expensive Express service for Prime orders and Ground for non-Prime shipments, according to Amazon.

FedEx said in a statement to CNN Business that the decision only affects a small number of shippers. But it said the move may impact these small sellers' ability to manage their businesses by limiting their options "on some of the highest shipping days in history."

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