Amazon shoppers in Los Angeles and New York will soon get USPS packages delivered on Sundays after the mail carrier and the online retailer announced a partnership, Monday. 

The roll-out will also continue to large portion of the U.S. population including Dallas, Houston, New Orleans and Phoenix in 2014. 

"If you're an Amazon Prime member, you can order a backpack for your child on Friday and be packing it for them Sunday night," said Amazon's Vice President of Worldwide Operations and Customer Service, Dave Clark. "We're excited that now every day is an Amazon delivery day and we know our Prime members, who voraciously shop on Amazon, will love the additional convenience they will experience as part of this new service."

Though it means that Amazon Prime members will get free two-day shipping all week-long with a subscription, deliveries for those not enrolled in the program will be treated "like any other delivery day of the week" according to Clark. Launched in 2005, the Prime service from Amazon allows free two-day shipping on all eligible purchases and a subscription to its Instant Video streaming for an annual fee of $79 a year. 

Considering the United States Postal Service lost $16 billion last year and ended Saturday mail delivery (retaining packaged delivery), this partnership couldn't have come at a better time. Reasons for the drop in revenue came from the disappearance of first-class mail and a law requiring it to pre-fund health care for its retirees in 2006. The Amazon deal could potentially give the struggling agency a much needed boost in revenue, as shipping and package revenue gre five percent thanks to growing populaity in online shopping.

"As online shopping continues to increase, the Postal Service is very happy to offer shippers like Amazon the option of having packages delivered on Sunday," Postmaster General and Executive Officer Patrick R. Donahoe said. "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."

Amazon share prices were down 1.46 percent at $349.20 during midday trading on Tuesday on NASDAQ.