Google is trying once again to capture some of the momentum surrounding social networking companies like Facebook and Twitter by adding new features to Gmail, its popular e-mail service.

Later this week, Google will introduce add-ons to Gmail that let users post and view messages about their day-to-day activities, according to a person at Google briefed on its plans. This simple tweak to Gmail will allow Google to mimic the status updates that have driven much of the success of Facebook and Twitter, as people return to the services again and again to check out what their friends and co-workers are doing.

To date, Google has allowed users to post only a brief message about their status through its Chat system, which is linked to Gmail. The new features would allow a more vibrant back-and-forth among Gmail users.

It is not clear whether Google will link the new Gmail features to rival social-networking services.

The Gmail move signals that Google remains serious about becoming a social media force at a time when some of Silicon Valley’s younger start-ups have stolen some of its thunder.

“It might look like a minor feature advance, but this is another blow in the war against Facebook,” said Jeremiah Owyang, a partner at Altimeter Group, a technology consulting company.

Google has a full-blown social networking service called Orkut that has proved especially popular in Brazil. It also has a web browser add-on called Sidewiki that lets people jot down and share information about a website, and a Profile service where people can post information about themselves.

Google is also expected to create strong ties between Gmail and its YouTube video site and Picasa photo gallery service. — © 2010 The New York Times News Service