Amazon was to announce Monday that it will begin Sunday deliveries using the U.S. Postal Service's fleet of foot soldiers, office workers and truck drivers.

To accommodate the online retailing giant, the Postal Service said it will for the first time deliver packages at regular rates on Sundays. Previously a shipper had to use its pricey Express Mail service and pay an extra fee for Sunday delivery.

The initiative will begin immediately in Los Angeles and New York and spread to much of the rest of the nation next year, Postal Service officials said. The partnership should help the turnaround effort at the financially strapped Postal Service, they said.

The arrangement with Amazon could open the door to more partnerships with retailers that are eager to use the 500,000 USPS employees and 31,000 post offices across the country to satisfy consumers who want to get what they buy online faster.