Google is adding e-commerce transaction capabilities to its Google Base service, providing a platform for buyers to purchase items from sellers using credit cards.

The plan is in its initial stages and only a "small number" of sellers are involved, but Google plans to extends its availability over the coming months, according to a posting on Friday on the Google Base official blog.

Google Base, which the company has been testing publicly since November 2005, is a service designed as a funnel for users to post all kinds of content to the search engine's index.

Google Base is meant as a complement to the company's 'web crawler', which goes out and indexes content from websites. With Google Base, users can feed the index with information the web crawler may miss or not be able to fetch.

Since a portion of the items posted on Google Base are for sale, Google has decided to facilitate those transactions. "To help users more easily purchase and sell Google Base items, we're planning to enable people to buy items on Google Base using their Google Accounts," wrote Chetan Patel, Google's engineering manager, and Stephen Stukenborg, product manager at the firm.

Google didn't immediately respond to a request for further comment about its Google Base plans.

When Google Base was launched, the firm went out of its way to explain that the service was aimed at users wanting to feed content to the Google index, and not at users who wanted to conduct searches. Data entered on Google Base, it said at the time, would surface in the company's various search services, such as general web search, comparison shopping and local.

"We're not driving [search] users to Google Base. This content will be searchable in some way from other Google properties," Salar Kamangar, vice-president of product management at the company, said in November.

However, it's not clear if this is still Google's plan for Google Base, considering the service is becoming an e-commerce platform on which transactions will take place. With the change, it seems to be morphing from a data repository designed to feed Google's search services into an online marketplace where buyers and sellers will meet, similar in nature to eBay.

The Google Base announcement is part of a larger effort from the firm to seed its services, where appropriate, with online billing and payment capabilities, according to another official Google blog posting on Friday.

"Looking ahead, we want to continue building payment services that meet the needs of users and advertisers. We expect to add payment functionality to Google services where our users need a way to buy online," wrote Benjamin Ling, product manager and Tom Oliveri, product marketing manager at the official Google blog.