The trial will begin in San Francisco and another city, said Brian Elliott, general manager of Google Express, which already delivers merchandise, including dry foods, to customers. Whole Foods Market Inc. and Costco Wholesale Corp. will be among Google's partners for the new service, he said.

"For a lot of our merchants that have been successful with this, we're not representing the whole store today," Elliott said in an interview. "It's in our incentive, as well as the merchant's incentive, for us to help customers get the full store delivered to them."
 
Google is investing in delivery services for homes and businesses as it seeks to lure more traffic to its websites. The move puts the company in more direct competition with Amazon, which has rolled out its AmazonFresh service in several U.S. cities. In April, a report showed the e-commerce giant was the lowest-cost among rivals in New York.