San Francisco ? Google Inc. opened a new social hub in its e-mail service on Tuesday, leaving little doubt that the Internet search leader is girding for a face-off with Facebook.

The new Gmail channel, called Google Buzz, includes many of the features that have turned Facebook into the Web’s top spot for fraternizing with friends and family.

It comes less than a week after Facebook made changes of its own. Among other things, Facebook now shows a list of friends available for chatting on the left side of the page, similar to where Gmail now displays its chat feature.

The Google Buzz features won’t reach all of Gmail’s estimated 176 million users worldwide for several more days. A link to the service will appear on the top left of the page, in a prominent position just under Gmail’s inbox tab.

Like Facebook, Google Buzz will let Gmail users post updates about what they are doing or thinking and share those with the rest of the world or with only a select group of people. Gmail users also will be able to track other people’s updates and instantly comment on them for everyone else in the social circle to see.

And, just like Facebook, Buzz can serve as a showcase for video, photos and Web links to interesting stories.

Google Buzz also shows similarities with Twitter, an online communications tool that broadcasts messages of up to 140 characters. A mobile phone application of Google Buzz is particularly Twitter-like: It allows people to see the public updates of other people in the same vicinity.

Some of Google Buzz’s features mirror social tools already available in instant-messaging services and other Web-based e-mail, including Yahoo Inc.’s. Google Chat, which is incorporated into Gmail, already has limited ability to display status updates.

Google launched a social network called Orkut six years ago, just a few weeks before Facebook began in a Harvard dorm room, but Orkut has gained little traction outside of Brazil. Meanwhile, Facebook has emerged as a cultural phenomenon with more than 400 million users worldwide.

Google co-founder Sergey Brin seemed confident that Google Buzz will enjoy broader success.

“Every couple years something new and revolutionary emerges and thanks to the Internet it can really emerge very quickly and affect many people in a short period of time,” Brin said. “I certainly hope that trend will continue and I hope we will make our own contribution with this set of capabilities.”

Without mentioning Facebook specifically, other Google executives predicted the new service will do a better job of sifting through the clutter of personal updates to pull up the ones most likely to pique each individual user’s interest.