Always trying its best to be the nation’s first choice for shopping, Amazon.com (News - Alert) has decided to deliver packages on Sundays in Los Angeles and New York starting this coming Sunday, November 17. This isn’t too surprising since the e-tailer has traditionally gone to great lengths to ensure a level of service that surpasses its competitors. The surprising part is that Amazon is launching this initiative with the help of the United States Postal Service (USPS (News - Alert)).

The fact that Amazon has recruited the USPS, however, only goes to show just how committed it is in outdoing its brick and mortar competitors. Indeed, Sunday delivery is just another way to beat traditional retailers like Best Buy (News - Alert) by offering greater immediacy. Last year, Amazon had to start collecting sales tax in various states, an advantage which it had enjoyed for some time.

According to Forrester (News - Alert) Research analyst Sucharita Mulpuru, Amazon is likely taking higher costs in order to accomplish this since the fact that lower deliver volumes on Sundays should equate to higher expenses. This is just speculation, though, since Amazon and USPS declined to comment on the costs or volume projections of the contract.

“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,” said Patrick R. Donahoe, Postmaster General and Chief Executive Officer of USPS, in a statement. “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.”

Not only will customers in New York and Los Angeles be able to enjoy Sunday shipping going forward, so will residents of London in the U.K. Next year, several more U.S. cities will also receive Sunday shipping, including Dallas, New Orleans, Houston and Phoenix.