Google, the world's most used search engine, is set to take on online voice and instant messaging service providers such as Skype, Microsoft and Yahoo.
The firm has released a free service called Google Talk, which lets e-mail account holders talk to each other via a PC, microphone and speakers.

There had been speculation that Google would use the cash from a $4bn share sale to buy its way into the market.

Instead, Google promised to try to make Talk work with other firms' offerings.

Google Talk will also offer instant messaging, but unlike other services such as Skype or Vonage it will not let users make calls to land lines or mobile phones.

'Missing piece'

Demand for online phone services is expected to surge in coming years as consumers look for cheaper ways of making calls and take advantage of quicker internet connections.

Google is looking at different ways of boosting its revenues, and last year started offering a free e-mail service to a limited number of users - although they are now allowed to invite an effectively unlimited number of people to join as well.

It makes money from the e-mail service, called Gmail, by placing small adverts along messages that are relevant to what is being discussed.

Similarly, earlier this week the firm launched an updated version of a tool to search PC hard drives, which ties in closely with its online search engine.

Google Talk does not carry adverts, but Google says it hopes it will drive people to sign up for Gmail.

"This is a missing piece in Google's larger strategy as they emerge to become a bigger internet media player," said Greg Sterling, an analyst at the Kelsey Group.

Google Talk will be based on open software, meaning the firm will allow its technology to be integrated into other websites and applications.

Google hopes that will encourage companies and individuals to expand its service and tailor it to better suit their needs.

Catch up

It also wants to offer users the ability to talk to people on other providers, something that some rivals with closed systems cannot do at present.

Analysts warned, however, that Google had a lot of ground to make up on its rivals such as Yahoo, AOL and Microsoft, which already have millions of signed up users.

A trial version of Google Talk can be found at: http://www.google.com/talk/.