The amount of time American users spend on Google's new social-networking site has grown more slowly in recent weeks, according to Experian Hitwise, indicating that the service may struggle to make headway against Facebook.
Users on average spent 5 minutes and 47 seconds on Google+ during the week ended August 27, up about 4 per cent from the previous week, according to Experian Hitwise, which tracks internet statistics. Time spent on the site peaked in the week of July 16, at 5 hours, 50 minutes, Hitwise said.
Google+ is the company's latest effort to compete against Facebook, the world's most popular social site.
While the new service had good features for sharing content with friends, Facebook was an entrenched rival with more than 750 million users, said Charlene Li, an analyst with Altimeter Group in California.
"The people that you'd want to add are in many cases very happy on Facebook and they don't want to have another social network," Li said.
US visits to Google+ fell 5.5 per cent to 1.16 million during the week ended August 27, after rising 2.6 per cent the previous week, according to Hitwise.
Still, Google hadn't opened up the service to everyone yet, so it was too early to judge user numbers, said Michael Gartenberg, an analyst with Connecticut-based Gartner.
"Early reactions from people who have used the service seem very, very positive. But we're talking about a service that hasn't been widely opened up, that most consumers can't get access to."
Google+, designed to help users share information with select groups of friends, debuted in a trial version on June 28 by invitation only. Since then, the company has been working to add more features. This month, Google+ rolled out a games service with developers such as Zynga and Rovio Entertainment Oy, creator of the hit Angry Birds.
Hitwise's research methods, which rely on visits to websites, don't include mobile users or times when people access the service from the black notification bar running across the top of Google.com.