Want in on Google Voice? Better start being nice to a friend who is already using the service.

That's right, Google, who is still struggling to meet invite requests for its Google Wave beta, is now letting current users dish out invites to their mates to get them in on the Voice service.

"Starting today, we're beginning to give out invitations to Google Voice users. If you currently use Google Voice, over the next few weeks, you'll see an "Invite a friend" link appear on the left-hand side of your inbox", said Google in a post on its official blog.

The service, launched earlier in the year, allows you to manage all your telephone numbers into a single number, your Google Voice one. Users are then able to manage their calls as well as make free national and cheap international calls from their web browser.

Google Voice is still only available in the US.