WASHINGTON (AP) - The cash-strapped U.S. Postal Service is moving aggressively this holiday season to offer same-day package delivery for Internet shoppers.

Teaming up with major retailers, the post office will begin the expedited service in San Francisco on Dec. 12 at a price similar to its competitors. If things run smoothly, the program will quickly expand next year to other big cities.

It follows similar efforts by eBay, Amazon.com, and most recently Wal-Mart Stores Inc., which charges a $10 flat rate for same-day delivery.

The delivery program, called Metro Post, seeks to build on the post office's double-digit growth in package volume to help offset steady declines in first-class and standard mail. It's projected to generate between $10 million and $50 million in new revenue from deliveries in San Francisco alone.

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