Internet giant Google has opened its Google Voice telecommunications service to anyone in the United States interested in using a single telephone number for all of their phones.

Google Voice reportedly attracted more than a million users during an invitation-only test phase and Google was bracing for a flood of interest on Tuesday as it made the service public.

"Today, after lots of testing and tweaking, we're excited to open up Google Voice to the public, no invitation required," product managers Craig Walker and Vincent Paquet said in a joint blog post.

"We're proud of the progress we've made with Google Voice over the last few years, and we're still just scratching the surface of what's possible when you combine your regular phone service with the latest Web technology."

Along with letting users have one phone number that rings at all of their telephones, the service converts voice mail or text messages into email and allows for toll-free calls to the United States and Canada.

In an online video describing Voice, Google promised "less annoyances and more awesomeness - for free." Voice threatens to challenge global Internet telephony star Skype.

People in the United States can sign up for the service online at

Google promises that the service works "no matter what kind of phone you have or which carrier you use."