Amazon to Begin Sunday Deliveries, Calls on USPS (NASDAQ:AMZN) said  it will partner with the U.S. Postal Service to start shipping packages marked for Sunday delivery.

The new delivery service date will start in the Los Angeles and New York metropolitan areas on Nov. 17 before expanding next year to Dallas, New Orleans, Houston, Phoenix and other cities.

Though they can select it, Amazon customers won’t be required to specify Sunday delivery, which will be offered for no additional charge. The nation’s largest online retailer recently said shoppers will see a Sunday delivery estimate when the service is available in their region.

Members of Amazon Prime, a $79-a-year subscription program that includes free two-day shipping, will receive eligible products on Sunday if ordered by Friday.

Amazon said it will transfer packages from its warehouses directly to Postal Service locations by Saturday evenings or Sunday mornings. The agency will then deliver the packages to doorsteps.

The Postal Service typically delivers packages on Sundays around the holidays, but the partnership with Amazon represents its first agreement to make Sunday deliveries on a regular basis.

By beating out UPS (NYSE:UPS) and FedEx (NYSE:FDX), the Postal Service will likely get a financial boost from the new contract. The agency, which has proposed eliminating Saturday mail delivery, expects to lose around $6 billion this year.

“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 Postmaster General and CEO Patrick Donahoe. “With this new service, the Postal Service is now delivering packages seven days a week in select cities.”

Sunday delivery isn’t new to Amazon. The company recently launched same-day and Sunday grocery deliveries in Seattle and Los Angeles, where it uses its own trucks to deliver items. Amazon will continue to let grocery customers include non-grocery items in the same shipment.

Amazon shares climbed 1% to $354.00 Monday morning.