Amazon.com will offer customers a one-hour delivery option for books, CDs and toys through a partnership announced today with Kozmo.com.

The leading online retailer has invested $60 million for an undisclosed stake in Kozmo, which delivers videos, food and other convenience items to shoppers. As part of its investment, Amazon says it signed a three-year strategic alliance to begin offering the new delivery option. Amazon did not specify when one-hour delivery service would be available. Kozmo currently operates in New York, Boston, Washington, D.C., San Francisco, Seattle and Los Angeles. The company expects to operate in a total of 21 cities by the end of the year, and is widely expected to file soon for an initial public offering. For all the convenience of shopping online, delivery has always been one of the biggest hurdles facing online retailers like Amazon. Many people hate to wait the three to five days it can take for a purchase to be delivered, and balk at paying premium prices for overnight delivery. Last year, Amazon rival Barnesandnoble.com tested a hand-delivery service of books in New York City.