WASHINGTON - The U.S. Postal Service says Los Angeles was the worst city in America for dog attacks on letter carriers last year, and it urged pet owners to help reduce the attacks. The agency on Wednesday released its city rankings ahead of National Dog Bite Prevention Week, which starts Monday. The Postal Service said nearly 5,900 postal workers were attacked last year, a tiny portion of the 4.7 million Americans bitten by dogs annually. Los Angeles was the worst with 69 attacks, followed by San Antonio with 42 and Chicago with 41. The city with the least attacks was Wichita, Kan., with 20. If letter carriers feel threatened by a dog, they can skip delivery to the house and ask the customer to retrieve any mail at the post office instead.