March 17 (Reuters) - Amazon.com ( AMZN ) is looking to sharply cut the number of packages it sends through the U.S. Postal Service, a move that could cost the agency millions of dollars in revenue, the Wall Street Journal reported on Tuesday.

The e-commerce giant, long considered the Postal Service's top customer, has been pulling back on its postal shipments and is looking to reduce them by at least two-thirds by fall this year, when its contract with the agency is set to expire, WSJ reported, citing people familiar with the matter.

Amazon ( AMZN ) and USPS did not immediately respond to Reuters' request for comments.