The report said that as Google attempted to boost its already lofty profits and become an even more prominent player in ecommerce, the company risked alienating one of its biggest advertisers, online auctioneer eBay, which ran the Internet's leading payment service, PayPal.
Although Google did not view its service as a PayPal competitor, there was no question it posed a long-term threat to eBay, said Internet market analyst Greg Sterling.
"Any time Google does something like this, it has the potential of turning into a big deal," he was quoted as saying.
The report said at least two merchants, Starbucks and Buy.com, that had signed up for Google's new service also accepted PayPal.
eBay spokeswoman Amanda Pires declined to comment on Google's entry into online payments, but the company signaled its concerns about the search engine's expansion last month when it formed an alliance with Yahoo that would make PayPal the preferred payment
provider on the Internet's most trafficked Web site, the report said.