The US Postal Service has entered a partnership with online retail giant Amazon to deliver its packages on Sundays for the first time. Amazon said Sunday deliveries will be an option for all its orders without an extra charge. Subscribers to "Amazon Prime" who pay a yearly fee for free delivery can also get Sunday delivery. The first deliveries will be in large US metropolitan areas starting in New York and Los Angeles, Amazon said in a statement on Monday. Sunday deliveries will expand "to a large portion of the US population in 2014," including Dallas, Houston, New Orleans and Phoenix, the statement read. The move is welcome for the US Postal Service, which has been hemorrhaging money for years. It currently delivers mail Monday through Saturday, and some packages for an extra fee on Sunday. "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 Patrick Donahoe. USPS tripled its losses in 2012, losing $15.9 billion as the state-owned enterprise faces tough private-sector competition and what it calls onerous and unfair retirement funding requirements. The postal service announced plans earlier this year to end Saturday deliveries to save money, but backed off amid opposition from lawmakers to the proposed service cuts. Sunday package delivery will allow the USPS to better compete with rivals United Parcel Service and FedEx, and to better position itself to tap into a boom in online sales.