Amazon customers in New York and Los Angeles will be the able to have their packages delivered on a Sunday, the online retailer announced.
The company announced on Monday that it has teamed up with the U.S. Postal Service and plans to roll the service out to a large portion of the U.S. in 2014 including Dallas, Houston, New Orleans and Phoenix.
"We're excited that now every day is an Amazon delivery day." said Dave Clark, Amazon's vice president of worldwide operations and customer service in a press release on Monday.
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The deal could prove to be a blessing for the U.S. Postal Service which has suffered 7 consecutive quarters of net losses as it struggled against parcel delivery companies FedEx, DHL and UPS.
The semi-independent government agency has suffered in recent years with the introduction of email and the drop in sales from stamps as well as a 2006 congressional mandate to pre-fund up to 75 years of its future retirees' health care.
Earlier this year, Postmaster General Patrick Donahoe made pleas to lawmakers to allow the financially troubled Postal Service to switch to a five-day delivery schedule for first-class mail in an effort to reduce costs to return the organization to financial stability.
Package deliveries - which was never part of this plea - continues to grow and Donahoe said in the press release on Monday that the Postal Service is very happy to offer shippers like Amazon the option of Sunday deliveries. Research on the websites of rivals FedEx and UPS suggest that the two companies do not currently offer a Sunday delivery service. Both were not immediately available for comment when contacted by CNBC.
"With this new service, the Postal Service is now delivering packages seven days a week in select cities. Customers can expect the same reliable and valued service that the Postal Service currently provides," he said.
This article has been changed from an earlier version to reflect a clarification from Amazon.
By CNBC.com's Matt Clinch. Follow him on Twitter @mattclinch81